Yeah I own the D2K and have owned the DT770 80 and 600 ohm. They 80 ohm and the D2K are similar, though the mids are a tad better on the DT770, the treble of the 770 is brighter but at the same time less sibilant sounding to me. The bass of the D2K is deeper and the sub bass is stronger, but also kind of flabby. The 770's is deep but not as deep, it has a punch but the impact isn't quite up to par with the D2K.
Now, the 600 ohm is totally different. It is much more close to balanced than the other 2. The treble is SO MUCH smoother, and the mids are more forward. The bass isn't as strong but it still goes just as deep as the 80 ohm if EQ'd a little.
The impact of the DT770 600 with Alpha Pads has bass impact close to the D2k, but still not the sub bass.