Denon AH-D2000's and Beyerdynamic DT770 Pro 80's are both incredibly comfortable. I give a slight nod to the Beyers since the velour is just so soft and breathable, but both are top-tier in comfort.
The Denons might be a little hard to find, unless you go used.
Also, not sure what kind of gear you have, but both sound great unamped.
EDIT: Er, maybe I should ask what kind of environment they'll be used in. The Denons are definitely not a portable headphone, and not good for loud environments. They're practically fully open, and their build quality, to me at least, doesn't inspire a lot of confidence. They Beyers definitely trump them in this area. But if they'll be used exclusively indoor, the Denons might be the better option, since I think they sound a little better.