Monolith by Monoprice M2100X Stereo Amplifier Reviewed

Few mainstream electronics brands offer such a vast array of products and yet still manage to maintain a reputation for quality, customer service, and value as the California-based Monoprice. Looking for a couple THX-certified dual 15-inch 2000-watt subwoofers for your listening room designed by Dr. Hsu? Perhaps you need some value-oriented, high-end planar headphones? Monoprice, again, has you completely covered. Maybe you have a need for a new folding wheelchair for Grandma and/or a disc golf set, and your 2023 Christmas shopping list could be complete. Monoprice can do all of this and more and all with the type of quality you might expect from a Costco Kirkland product (Macallan makes their Kirkland Scotch and the parent company of Titleist makes Kirkland golf balls) in that all-star designers often are behind Monoprice’s audiophile gear.

One might expect that a brand with so many products across so many product lines could not possibly produce audiophile-worthy components and speakers. This couldn’t be further from the truth, as Monoprice (more specifically Monolith, Monoprice’s high-end audio/video sub-brand/entity) continues to disprove the skeptics and impress the audiophile community by producing a handful of winners every year or so. Case in point, the new very budget-friendly yet powerful two-channel behemoth power amp: the Monolith by Monoprice 2100x Stereo Amplifier, which we will explore in this here review.  

What Makes the Monolith by Monoprice M2100X Stereo Amplifier So Special? 

• The Monoprice M2100X (buy at Amazon) is arguably the best traditional two-channel class A/B amplifier under $400 on the market today. It features two channels of amplification at 90 watts per channel into eight ohms, as well as two unbalanced RCA and XLR inputs. It produces clean power with minimal distortion in a quiet, heat-controlled housing that is unmatched at this price point. Its 0.02-percent total harmonic distortion rating (THD) and signal-to-noise ratio around negative 100dB are extremely impressive for this price class. 
• The Monolith by Monoprice M2100X is an attractive-looking amplifier that will blend in with any system. Its brushed stainless-steel façade and single illuminated power button are not meant to draw attention, but it looks and feels well-built and of far higher quality than its price tag suggests. 
• The Monolith by Monoprice M2100X Stereo Amplifier is rumored to be secretly designed in part by industry legend Morris Kessler. Kessler is perhaps best known as the designer for ATI amps, but has OEMed some amazing amplifiers for various brands, such as Mark Levinson, Integra, Lexicon, and Outlaw Audio. Knowing that an industry heavyweight such as Kessler may have likely had a hand in the design of this line of amplifiers should assuage any fears of subpar quality.
• Monoprice offers an excellent customer service value proposition, including a three-year warranty, 45-day money-back guarantee, and 60-day price protection. This combination is rare in the industry and exemplifies Monoprice’s commitment to customer satisfaction. While the M2100X is not high-priced by any means, those new to the hobby and/or with limited budgets will find comfort in knowing their component is protected for at least a few years. 

Why Should You Care About the Monolith by Monoprice M2100X Stereo Amplifier?

There are subtle nods to much more expensive amplifiers on the surface and hidden within the Monolith by Monoprice M2100X. At $399, this is unexpected but welcomed. This, combined with a sturdy build quality and an impressive stat sheet, makes for a unique and valuable benchmark amplifier for truly any HiFi enthusiast. The Monolith by Monoprice M2100X is far from perfect, but overdelivers on so many fronts that it will undoubtedly develop into a fan favorite, especially as the competition in the sub-$500 class A/B amplifier category continues to thin.  

Some Things You Might Not Like About the Monolith by Monoprice M2100X Stereo Amplifier

• The Monoprice M2100X is about as basic as they come in terms of audiophile power amps. The design, functionality, and connectivity are no-frills, by design. Those wanting more at this price point could likely be persuaded to purchase an affordable integrated amplifier or home theater receiver, likely at the expense of sound quality and sheer power. 
• There is nothing fancy about this amp’s physical appearance. As previously stated, this amp was clearly designed to disappear into a rack or under other components. If you are looking for high-end finishes, sexy display screens and artisan-inspired knobs and dials, this may not be the amp for you – just be prepared to double or triple your budget.

Listening to the Monolith by Monoprice M2100X Stereo Amplifier 

I powered my SVS Prime Pinnacle Floorstanding Speakers with the Monoprice M2100X 2-Channel Amplifier, paired with my Schiit Modi 3 DAC and Adcom GFP-915 Stereo Preamp.  All music was streamed through QoBuz at max settings and connected directly through my Asus ROG Zephyrus G14 laptop.  

For my first track, I decided to go black metal on black metal. On the 10-year anniversary reissue of their brilliant album Sunbather, Deafheaven goes all in on the expansive opening track “Dream House” (Hi-Res, 24-bit, up to 192 kHz. I pushed the Monoprice M2100X hard during this session, and it handled everything I threw at it without breaking a sweat. There was minimal breakup or struggle, even as the crunchy, dense metal guitar challenged my system at high volumes. George Clarke’s intense vocals can be painful on inferior amplifiers and some ears, but not the Monolith by Monoprice M2100X. Another highlight for me was the sheer explosivity of Daniel Tracy’s drumming. The snares snapped with utter authority until the very end. For the purposes of comparison, I listened to the same track on my PS Audio Sprout100, a class D amplifier that puts out 100 watts per channel, similar to the Monolith by Monoprice M2100X. The Sprout handled the track equally well, but with slightly less crispness at higher volumes. My subjective preference definitely leaned towards the M2100X, which I have now anointed as my go-to death metal amplifier. 

Hiroshi Yoshimura’s album Surround, originally released one year after I was born in 1986, received a proper reissue in 2023. The track “Something Blue” (Hi-Res, 24-bit, 44.1kHz) is quite the contrast to my first listening selection, but one I revere for its simplicity and texture. The Monoprice M2100X unsurprisingly produced clean, distortion-free listening, and highlighted the various shades of color this track evokes, including deep, neutral digital bass lines, accompanied by glitchy, mid- and high-frequency riffs. Spatially, the M2100X provided a confident, emotive presentation with minimal noise or coloration, and allowed the song to shine on its own. Clarity was also impressive, showing that power and accuracy go hand in hand with this amplifier – something I expected, but not quite to this degree.  

Will the Monolith by Monoprice M2100X Hold Its Value?

At $399, you likely aren’t purchasing the Monoprice M2100X with the intention of passing it down to your grandchildren as a family heirloom. But because Monoprice’s reputation has grown and evolved over the years, I often see their gear for resale on Facebook Marketplace and eBay at close to (and often better than) 50 percent of purchase value. There is also a significant amount of internet chatter about this line of amplifiers by Monoprice, allowing it to gain a bit of a cult following. Therefore, it stands to reason that future audiophiles would target this gem on the resale market in the near or even distant future, which bodes well for its long-term staying power and retained value. 

Who is the Competition for the Monolith by Monoprice M2100X?

• The Emotiva BasX A2 Stereo Amplifier  is a strikingly similar class A/B stereo amplifierpriced at $499 that offers slightly higher power specs at 160 watts per channel into eight ohms and 250 watts per channel into four ohms, with a rated total harmonic distortion (THD+N) of around 0.02 percent, and a signal-to-noise ratio of 112 dB. It features a near-identical look and feel, albeit for $100 more than the Monoprice M2100X. 
• Another interesting option in this price class is the $399 Cambridge Audio AXA35 (buy at Crutchfield). This is another class A/B amp that features additional connectivity options, such as USB for a Bluetooth adapter and a phono stage, as well as a slightly more refined look, but at the expense of power. The Cambridge Audio AXA35 only puts out 35 watts per channel into eight ohms and, while this is more than enough for most setups, the Monoprice M2100X offers significantly more pure power at the same price point. 
• A Chi-Fi competitor in this price range is the S.M.S.L. SA400 High Resolution Power Amplifier. The SA400 is a class D integrated stereo amplifier that puts out impressive power at 230 watts per channel at four ohms and claims impressively low distortion at 0.0002 percent. It also features Bluetooth 5.0/APTx connectivity and a dedicated remote control for those looking for a more connected, integrated experience. That said, it isn’t the best-reviewed sub-$500 class D amplifier on the market, and may not suit the tastes of more traditional audiophiles looking for classic A/B power and sound, and who might prefer a more understated look. 

Final Thoughts on the Monolith by Monoprice M2100X Stereo Amplifier

The Monolith by Monoprice M2100X Stereo Amplifier is an excellent value for any audiophile, but especially those on a tight budget. Whether you are in the market for the first building block of your stereo setup, or searching for a budget-friendly two-channel beast for a secondary system, the Monolith by Monoprice M2100X represents the perfect blend of economy, build quality, and thoughtful design. 

In researching and writing this review, I truly struggled to find a competitor on the market today that manufactures a product at this price point with so many pros and so few cons. Undoubtedly, there are prettier and pricier options that would achieve the same result, but for those seeking simplicity and pure power at a discount, you can’t go wrong with the Monolith by Monoprice M2100X Stereo Amplifier. And you sure as hell can’t beat the price.