I got my MA 900 a month ago for 239$ from Amazon, Using it with FiioE17. I bought it after watching Lachlan's review on youtube along with some research on head-fi of course.
It was less comfortable initially than I expected, had itchy ears because of ear pads that settled in 2 days. I think its very lightweight but could still be uncomfortable for some. Given all the hype about ultimate comfort, I was expecting more .. so please give it a few days, It is now very comfortable for me.
Sound is , however, a different matter. Its just wonderful from the start, a lot better than I expected ( Lachlan called it a headphone for "everyday use", that lowered my expectations). Bass and mids are just delightful with good amount of detail and decent clarity given the signature. Some mid bass hump noticeable at times but overall very nice balance for my taste.
Treble is gentle but that is how I prefer it. Easily EQable for increased presence
Very non fatiguing even at louder volumes.
Very easy to drive
But the best aspect of its signature is the huge soundstage. Its very well defined, I watch a show with live music performances and its as if I am in the studio. I can locate everything with eyes closed. Instrument separation and imaging is great.
Very good movie headphones because of good bass and vast soundsatge.
Only gripe is build quality. I love the sound but I know its not going to last given the flimsy build, I will break it somehow. I wish Sony will come up with newer version with Velour pads and better build by that time. That would be just perfect.
Given all the similarities with the big boys, I may upgrade in distant future to HD 600/650 if I decide to buy a better amp but right now, I am very very happy with MA 900, It brings a smile on my face every time I pick it up. Life is good when you live with something you really like.