Yes, it is apples to oranges, but once I ate that juicy orange I swore off the apple forever, lol.
3xBlah, I'll check out your thread and post there, but I don't have much experience in that price range. I've been away from the hobby for a bit, so I'm not sure what's out there and what's new.
Comparing the HD650 to the DT880, I LIKED the 880s, but they were very neutral almost to the point of bland. They were amazing with vocals and acoustic music, no sibilance, nice rolloff on the top end, solid at the bottom, but not as detailed in bass response...very nuanced and smooth, great imaging...a much more forward presentation compared to the laid back 650s, almost like the performers are right in front of you. The 650s are very lush and warm in comparison, with a more wide open soundstage and sense of airiness. If I had to choose another headphone other than the 650s, I'd definitely give the 880s a much longer look. I infinitely prefer them over the dry and sterile AKG K701s, but I like the Denon D5000 a little bit more maybe, just for the music I listen to (rock, techno, etc.). The 880s for sure if I listented to more blues, jazz, vocals, or acoustic stuff.