My Audio Technica A900 headphones made it five and a half years of pretty much constant daily use (maybe 10-12 hours a day).  But in the last few months the arm holding the ear cup to the band has failed on both sides so I think it's time to retire them.  I wanted to try something new, and have settled on the AKG K272 HD.
 
Moving from the ATs, which I would say are easily the most comfortable headphones in the world (possible the entire galaxy), to the AKGs, am I going to be let down by the comfort and quality?  Also, will there be a noticeable difference in sound quality when listening to classical and acoustic music? I know the AKGs are very flat and neutral, which I think will suit me very well.
 
My other options that I'm only slightly considering are the Denon D1100s, Beyer DT770-80, and maybe the Ulrasone HFI-780, but I've heard that they can be a bit uncomfortable, and long term comfort is a high priority for me.
 
Thanks for any info and impressions you can give me.