I just got my MDs in! Wow! Much better than I was expecting. The highs that were missing from the HD650 are back! The mid-bass hump is gone. I wouldn't call these particularly dark. The bass seems very (slightly &) pleasantly emphasized. Sounds perfect out of my Asgard. I didn't bother changing my Amperex tubes from my Lyr (these give me low lows and high highs), and the bass is a little too much out of the Lyr. I'm sure I could find a set of tubes from my collection to make the MDs sound perfect from the Lyr. Versus the DT880, I'd say the mids are superior, the bass is, of course, superior, and the highs are crisp but not as overbearing as the DT880. Do these benefit from burn-in?
The soundstage is not that of an open phone, but not bad for a closed can. And isolation!! These aren't quite in the same league as the HE-500, but considering they cost less than half as much, the performance is fantastic. These blow away the Senn HD25-1 ii. The highs sound crisper than the HD600.
Alright, time to give these a workout and see how things fallout after the honeymoon.