I'm running a revo 7.1 -> ppav2 -> dt 880 or 325i
Personally, I feel that the source and the amp are a bit bright. I really should get around to finishing off my dynalo...
I have to turn the volume up on the dt880 vs the 325i; usually looking at a ~45 degree increase to get a similar volume level.
To my ears, the dt880 sounds great a high volumes but at low sounds, well, "sweet", for lack of better words. No real hard, sharp sounds and the entire freq response is smooth.
I seriously feel that the sr325i sounds far better up louder than softer. At low volumes it's good, even great, but the dt 880 just sounds better to me. I have to say that I'm not entirely happy with my 325i's sound though. The upper mids seem to be a bit recessed. I may have been a bit spoilt by the upper mids of the DT 880 though.
Incidentally, cymbals (highhat and crash) sound more defined on the DT 880 than the 325i but the 325i have more of an impact. Bass on the 325i is more... "exciting"...