I have Astro A40's now, and I can say for me, they are the best. they are extremely customizable and can be used with everything - truely everything you can throw at it. Just make sure to get the MixAmp with it. The sound quality is amazing, and I can use My Xbox 360, iPod, TV, and Computer games all with it. If you want only xbox 360, The Turtlebeach X41's are fine. They have nearly the same Sorround sound (But they are missing Dobly Logic partnership), and their Bass is better than an A40's.
Hope my comparison helps. Remember, with headphones: You get what you pay for. (More money = better 99% of the time)