Hmm.... I think the AD900x is very very confortable as it is. One thing I don't like is the two "bands" that goes on top of your head is a bit too loose, feels like the headphone is always dropping down.
It's my only pair of open headphones. While having a decent sound stage (after heaing the HD800 and the SR900 in a meet my standard is sky-high), the sound signature is a bit too "lazy" or "laid-back" for me, a bit muddy in the mids and bass... Vocal is amazing but "mechanical" sound effects like swords clashing or bullet hitting walls is not so great. I think it is regarded as one of the best phones for classical music, but personally I am more clined towards a very, very detailed sound.
Expecting a Etymotic HF5 IEM in the following week, it is praised for its isolation and detailed sound, can't wait to try it!