Just like this Massdrop x THX AAA 789 amplifier, the Monoprice Monolith Desktop Headphone DAC/Amplifier (with a THX AAA 788 amplifier built-in) hasn't been released yet.
Similarly, the Monoprice 788 features THX AAA amplifier technology... and adds an up-scale DAC, a full array of digital inputs, Dirac Sensaround processing, and a front LED display. While its complete specifications have not been revealed, a member of the Monoprice staff responded to a customer's inquiry regarding power output:
300 Ohms: 648 mW
32 Ohms: 3180 mW
16 Ohms: 1591 mW
The numbers likely correspond to its XLR balanced out - not its 1/4" output. So while the Monoprice 788 amplifier section is not powerful as the Massdrop 789 amplifier, it should still be powerful enough for all but the most power-hungry headphones.
For $130 more, the Monoprice 788 should be an excellent option for those looking for an above-average DAC/amp combo with a fair amount of power on tap, various inputs/outputs (including a balanced-out), and Dirac Sensaround processing - which could be a game-changer for headphone listening if it performs as described.
Information copy-pasted from the Monoprice Monolith Desktop Headphone DAC/Amplifier product page:
The Monolith Desktop Headphone DAC Amplifier features cutting edge THX AAA technology to bring out the best in your headphones, playback device, and music library. It utilizes the THX AAA-788 amplifier design for an impressive 2x1500mW of high-powered amplification with the world’s lowest distortion and noise. It also features the new flagship AKM AK4493 32-bit stereo Premium DAC with VELVET SOUND™ technology, Dirac Sensaround II decoding for an expanded larger than life soundstage, and a host of balanced, unbalanced, and digital inputs and outputs to ensure users have plenty of ways to connect their playback devices for a high-quality listening experience.
THX AAA Technology:Reduces harmonic, intermodulation, and crossover distortion by 20-100x for an unbelievably realistic and fatigue-free listening experience, and can reduce power consumption by a factor of 10 for incredibly long battery life. It accomplishes this using a patented topology to null conventional distortion mechanisms and reduce bias current.
AKM AK4493 DAC: The AKM AK4493 is the new flagship 32-bit stereo Premium DAC. Digital input supports PCM inputs up to 768kHz and DSD input of 2.8MHz/5.6MHz / maximum 11.2MHz the industry's highest level. Internal circuit employs a newly developed 32-bit Digital Filter for the ultimate in sound quality and musicality.
Dirac Sensaround II: Music is usually mixed with loudspeakers in mind, not headphones. As a result, headphone listening is often plagued by a distorted soundstage—instruments and voices may seem incorrectly placed and trapped inside your head, causing an unnatural listening experience that can result in listener fatigue. Dirac Sensaround II takes a different approach. Listeners can enjoy their favorite media in a way that seems to spread instruments, voices and objects out into space, enveloping the listener exactly as the artist intended. Dirac Sensaround II creates a vast, clear and realistically immersive soundstage free from the constraints of the space in your ear, much like a multi-speaker home theater system. This feature can be toggled on or off.