I've been using the Grace m9xx (Massdrop version of the M900, only difference being the m900 has coax input) for going on 5 years now. I buy/sell audio equipment very often, always trying new things. But the Grace has stayed. It's outlasted every other dac and amp in my collection. Why? I've yet to find anything that matches it's overall package of great sound, great form factor/build/size, and versatility.

First off the dac section alone competes with anything i've heard in the $500 or less range. The only dac i actually think sounds BETTER than the Grace dac around $500 is the Soekris dac1321. Anything else imo sound as good or worst. So bottom line, you're getting a VERY good dac that holds its own with anything else in it's price range.

Second, the amp section is very underrated. I can't say it can compete with anything in the $500 range, as there's some killers out there (Asgard 3, Lyr 3, Lake People RS-02 or G109S, Audeze Deckard, Beyerdynamic A20, etc.), but it holds it's own, and doesn't give up too too much to the better amps. As long as you're not trying to run very power hungry headphones through it (Fostex t50rp models, 600ohm Beyers, etc), it's a fine amp.

Third it's built like a tank, is very portable, and is very easy to use. I can't stress enough how nice it is to be able to take very high quality sound anywhere i want to go, including my own home! i have two small kids, so being able to move a high end dac/amp around the house as needed is beyond invaluable. and after 5+ years, my m9xx still looks great. it's got some wear, for sure, but i'm not very gentle... and it's still 100% fully functional.

Finally, being a combo unit, it's incredibly versatile. i often use it only as a dac, as i LOVE how the dac alone sounds with superior amplification (we're talking $1000 plus amps). but i also take it with me on trips, as i can easily use it in a hotel room, or even on an airplane, if i have a power bank available to power it (iphone alone cannot power it, you'll get the "device draws too much power" message if you try to just use a phone on it without the secondary power plugged in).

So as you can tell, i'm a huge fan of the m900/m9xx. I've tried countless combo units that compete with it, and nothing compares. i just don't see myself ever parting with it, it's been a constant in my ever changing audio equipment lineup. i originally started writing this review with a frequency response mindset (bass sounds like this, compared to that...blah blah blah), but found it didn't do the m900 justice. if you want to know a lot of fine detail on what it sounds like, other reviews will do a better job. all i'll say is as a combo, it's on the slightly warm and smooth side. a touch of treble roll off, a touch of bass boom (not a lot mind you, it's still great bass), smooth and non fatiguing mids. all in all a very engaging and inoffensive signature. going to dac only (with a separate, higher performance tier amp) , the smoothness is still there, as is the warmth, but gone is the boominess and roll off. the dac is capable of incredible resolution and extension, and really shines with a higher level amp. the internal amp, though decent, is definitely the weakest part of the package.

Looks great. Sounds great (neutral, easygoing sound). Easy to use. Ergonomic. Plenty of power for headphones.

Great features, including crossfeed, mono, channel balance adjustment, and much more.

I have the M9XX version of this and it sounds amazing. I have tried many brands and this is one of the best I have heard. I believe you have to step way up in price to beat this combo unit.