i dunno if i'd call the D2k lush and warm. it was v shaped, but very well balanced and with great sub-bass and sparkly treble. either way, the D2k is many times better than the D600. i've been considering buying back a pair of the old denon line sometime this year. maybe a d2k for fun and movies, or another d7k/th600/900.
Do you really feel they are many times better? I have them both and I'd agree the D2K is better but not by a lot (and my D2K is MarkL modded with angle pads so kind of the pinnacle of the D2K lineage). Have you listened to the D600 much?