(Note, I will be using a Creative Sound Blaster X-Fi Fatal1ty Professional with either headset).
Edited by Mrtaste - 10/20/13 at 3:34pm
I used the A50's for a few months about a year ago on an xbox. I'm just a casual gamer, FPS mostly. I thought the A50 setup worked pretty well with their mixamp simulated surround and chat functions. I have a 7.1 home theater setup and I thought the sound cues through COD/BF were similar between my speakers and A50's. I stopped playing in a clan and didn't need the chat functions so I sold it and went to using my other headphones & receiver for simulated surround for evening games.
I like a good amount of bass for FPS and as I remember it the A50's were adequate. I had Q701's but to my ears they're lacking the bass I want for games. I never directly compared the two though.
I voted A50 in your poll.
Might consider selling off the Fatality Pro and getting the Creative Sound Blaster Z (SB1500), $100.
and then see what your willing to budget for headphones.
The Z has a headphone amplifier, the Fatal1ty does not.
The Z's CS4398 DAC chip is better then the Fatal1ty Pro's CS4382 DAC chip.