these guys are mostly right with the d2000 being the better headphone.
the dt770 pro (im talking about the 80 ohm version which is the bass heavy model) has ALOT of bass. mostly lower middle bass and sub-bass. however, the low end does eventually roll-off. there is alot of bass, however, the denon d2000 comes very close to the same quantity. also, the denon seems to go even deeper and give more rumble if the song has alot of sub-bass. the dt 770 pro will have slightly more mid-bass than the d2000, however, neither emphasizes the upper and mid bass very much. also, the dt 770 tends to leak more of the bass into the mids. the mids are very recessed on the dt 770, however they are still smooth and detailed. the denon has better mids that are only slightly recessed and slightly less detailed. both headphones emphasize the treble and have a sparkly end. the denon are less bright than the beyers . after burn-in, both will still seem a little bright on the treble, but the denons definitely less so.
soundstage is bigger on the beyers, a little more smaller and forward on the denons. detail is very good on both cans, i can say the beyers have a little more detail in the high. everything else is the same. except the denons tend to have more bass texture and detail, overall the denons have cleaner bass. however, it can still get muddy and bloaty if you boost the bass too much, the denons however also get louder than the beyers do. separation is somewhat better on the dt 770.
overall, i think the d2000 is the better can.
i currently own d2000 and have sold my dt 770 pros a couple months ago.