*** updated with impressions ***
This is A LOT more comfy than the HD6xx. The bass on the MA900 may be the deepest for Open design. With electronic music, the bass goes deep. Sound signature not neutral like a AKG K701. It has a slight upper midrange bump like most Sony headphones. It's not bad at all. It's just Sony sound signature. I personally like it. I think the key feature is comfort. It's very very light and can be worn for hours on.
I don't think a in-store audition will show much of it's features and sound. You really have to spend some alone time with it without distractions.
Edited by HiFiGuy528 - 5/27/12 at 8:47am