Heya,
I completely do not understand how the AD700 comes up any time a gaming thread starts/ends, but it does. Is it an ok headphone? Sure, it is. Is it a good headphone for $100? I don't think so. So if it's actually worth $100 to you, ask yourself if you want to do anything other than play competitive-online-footstep-listening, such as listening to music or enjoying a non-FPS game, or even a FPS game that is story based (Crysis or Fallout or something). There's a detailed review of the AD700 in my signature if you click the model number. The AD700 basically has one thing going for it: it's got a huge 3D like sound stage that is pretty unnatural sounding, but is good for games. Other than that, it's just not a $100 headphone to me. But, don't let me sway you, I'm sure there are a lot of AD700 White Knights coming to the rescue soon.
The beauty of a lot of headphones that are not factory-crippled (like the AD700) is that you can equalize the bass down for FPS games for competitive-foot-step-listening. Then when you want the bass back, it can be there. This is much easier than trying to add bass to a headphone that lacks it (like the AD700).
Also, I assume you already have Dolby Headphone (sound card with that specific capability or something like an astro mixamp) for the actual positioning? Because if you don't, the AD700, nor any headphone, is going to magically provide surround sound and all of this will be rather pointless since you won't be getting any advantage to wearing any headphone over another, other than strictly sound quality and sound pleasure. Positioning has to do with a headphone's sound stage, imaging, and then the rest is all up to if you're using Dolby Headphone.
If you're on a budget, here's some suggestions:
Panasonic HTF600 (1/3rd to 1/2 cost of AD700); equalize the bass down and you have an interesting large sound stage headphone that is smooth and comfortable to wear, ready to bass it up when you want for music/movies/games/fun.
Samson SR850 (~ 1/2 cost of an AD700); everything the AD700 has, for half the cost, and has the bass of a normal headphone.
Fischer Audio FA-011 (equivalent cost of AD700); a really quality headphone, good natural sound from top to bottom, good imaging, comfortable. If you ever consider the AD700, you should hear a Fischer FA-011 first (albeit a difficult task).
Anyhow, maybe the AD700 is for you. If all you want is a huge 3D sound scape for foot step position listening with factory-crippled-bass, then the AD700 will definitely do that with no fancy equalizing or software. But if you want anything more for your $100ish, like a complete headphone, good sound in all ranges, no floating wings that touch only the sides of your head, no massive pads that fall off your head if it's small/narrow without serious bending of the headphone, then maybe consider researching a lot more headphones before committing to a purchase.
My suggestion to you is to get a Fischer Audio FA-011 for $118.

Very best,
Edited by MalVeauX - 11/23/11 at 10:00pm