ok, had the a900x for a few days now. My main issue is that the spring tension on the wings is very light, causing the wings to be very loose and not offer much support. I ran into this on a w1000 as well, while some audio technicas seem to have very stiff wings (my regular a900 is perfectly tensioned)
I tried putting a rubber band or a pony tail holder between the wings. once i got one of proper size and tension (basically adding just a little tension), the fit was great. this actually helps with the pad issue as well, as the pads are now resting against your head instead of pulling on your ears. still think the pads are kinda cheap feeling tho.
I also tried some creative labs wow headset pads (15$ from their website), which are large cushy pads, the comfort increased, clarity and stage increased slighly. sub-bass response went down slightly.
so, overall, love the sound, really needs more spring tension in the wings for support purposes