Well I was trying to hold off on comparing the two headphones side by side, but I caved this evening. Here are some of the basic things I've noticed between the two:
D7000:
Positives:
--Slightly better detail
--A tad better at resolving micro-dynamics
--Definitely more comfortable
--Soundstage is slightly "deeper", more expansive
Negatives:
--Bass is a bit overwhelming when listening at the same higher volumes as the HD650
--Bass is prominent, but slightly muddy
--Midrange is certainly recessed
--These headphones tend to "draw attention" to the sound they produce, AKA the "hi-fi" sound
HD650
Positives:
--Lush harmonic textures on piano, strings, and the harmonies between instruments
--Bass is tight, impactful, but not overwhelming
--While not as expansive, the soundstage feels more natural
--Reveals layer upon layer of timbre and texture, very rich, full sound
--Allows you to really enjoy the music rather than paying attention to details
Negatives:
--Treble extension not perfect
--Not quite as "transparent"
--Not as much "air" around the instruments
--Not as comfortable
Overall I think it's easy for me to say that at this point in time, I enjoy the HD650s more than the D7000s. I would not say that either one is superior (as I previously stated the D7000 was superior after my first experience with the HD650s a few years ago), but the are just different flavors. I feel that the D7000s are slightly more "transparent" or resolving simply because they have a hiked up treble.