I'll weigh in on the Denons as well. Th D7000 is a brilliant headphone in my opinion, but pricey at north of $600 even used most of the time (I think there is a pair on the FS sight for $580 right now?). That said, the D5000 is also excellent, and to me, the D2000 is very close to the D5000. Close enough for me, that between the two, I would choose the D2000. The Denon's don't leak out too badly, but outside noise does leak in pretty easily - though it was never an issue for me. The Pico DAC / amp combo pairs nicely with the Denons.
Another choice I haven't seen mentioned yet is the DT1350. Very portable, well built, bood bass, nice balance. It isn't perfect by any stretch though. Pricy for portables, not all that comfortable, some say timbral issues, though I love mine.
Ultrasone also has among others, the HFI 780, Pro 750 and Pro 900. I haven't tried the 900, but the HFI 780 fails on comfort and being really, really brittle/shrill/ bright. Same for the 750's - both again in my opinion. Others do like them. I've been curious about the 900, will probably try them someday. They will have similar comfort issues though. The midrange (anything below the "Editon" series) seem to use a similar frame that squeezes fairly hard, and has a stiff, narrow pad for the headband that quickly feels like a fulcrum digging into my head.