@rsf507, compared to my previous DAC at the time a SimAudio 380DSD I found the M3 a little lean. I liked the M3 and thought it had a little more detail and soundstage, and way more bass and dynamics than the much older SimAudio, but I desired a little more fuller presentation. I really liked the SimAudio DAC when I purchased it years ago as it had a very organic musical sound that didn't make me feel like I was listening to digital.
I didn't find the M3 to be analytical or fatiguing, I just wanted a little more meat on the bones... The RME I found to be cut along the same lines as the M3 sound wise, detailed and easy to listen to, it just didn't offer the same level of detail and soundstage and was likely the least dynamic of the DACs I tried (still killer for the $$ though in my opinion). The Mystique I think gives up a little resolution and maybe soundstage to the M3, has equal or maybe better bass/dynamics (its power supplies are pretty crazy), but has that organic/musical presentation of the SimAudio taken to another level.
The couple really cool features of the M3 though which add to its value in my opinion are the quality of it analog output (which almost matched to my ears my ~ double the price preamp) and its option for a $1K Ethernet streamer. I use a Bricasti M5 with my Mojo and it sounds excellent, but it costs more than $1K :)