i found this thread from a google search, noticed it's kinda recent, and just wanted to add my 2 cents.
I've had one pair of Audio Technica ATH-AD700's for about 7-8 years now, and they are my favorite headphones ever.
I'm as bass-head as they come. I listen to hip hop, post dubstep, and experimental bass music. The stage on the 700's is more important then their bass response. I also own some ATH-M50X's and.........I hate them. They may have better straightforward bass RESPONSE but........ bear with me....... the bass STAGE is more important. The 50X's produce more electric signal in the sub 500 range, sure, but it SOUNDS worse. Bass just sounds HUGE on the 700s. More like you're in a club with massive woofers. The 50X's sound like you have super loud speakers strapped directly to your ears.
For this reason, the 700's are also MUCH less fatiguing to listen to for extended time. better for just about everything. movies, gaming, music, everything i can imagine. TBH i hate the 50X's. They sound weak and pathetic compared to the 700s. I understand they don't make the 700s anymore, and have replaced them with a "700X" version. I can't vouch for these but maybe someone else can