For those pairing the M-Stage with the D7000, I noticed a little something. It's commonly recommended to go with a gain setting of 10 with the D7000's, but I believe that if you have a MarkL modded D7000, the gain setting of 18 is better. I've noticed that the gain switch 10 has more of a focus on mids and rolls off the bass and highs a bit. While this would be great to balance out the stock D7000's, the MarkL Denons have already been somewhat balanced out, which makes the gain switch 10 essentially balance it out twice, and make it somewhat bass shy and less exciting overall. Switching the gain to 18 brought back the excitement and gave it back the Denon signature. If you think the Denons (MarkL or stock) are a bit too bassy, set the gain to 10, but if you like them the way they are, stick them on 18. Or, even better, try both!
Got these into my stable as a "downgrade" HD800 amp, replacing my good old WA6SE. The 6SE is better, without a doubt, but the reason I downgraded was because HD800 was no longer my primary headphone (the Stax 007 MK1's are) and I needed to come up with some money into furthering my Stax rig.
With that said, In my Macbook air -> M2tech Hiface -> Stello DA100 -> M-Stage (stock default version) rig, the HD800 sounds very lively and powerful, and am very satisfied with the synergy thus far. The main differences are that the M-Stage is little bit more harsh in the sibilance region and is less warm in the lower midrange compared to my old WA6SE, but these problems are not severe enough to my ears to become an issue. For the price it sounds spectacular indeed, and beats out the other SS amps I had such as the Stello HP100 and Burson 160D for the HD800. It's neck and neck with my old AMB M3 as well, which also amped the HD800's very well. Another plus is that it's very silent overall without hissing noise or static noises when I plug and unplug the headphones.
The only thing I'm not happy with, however, is its volume control. No idea why they decided to use a knob so slippery on this? Does anyone have a good recommendation on a nice tactile feel volume knob replacement?
The M-Stage should sound very good with the HD800's. According to the reviewer, the M-Stage is a fairly close knockoff of the Lehmann Black Cube Linear, which was paired with the HD800 during its development and after during demonstrations at trade shows. So in a way, they were almost made for each other. ;)