If its for Xbox, I think any can play at the same time. Unless your looking for a way that you dont have to use the music from your hard drive?
What TB's do you own, and what are you looking to spend? I've owned a couple of Trittons, Stopped at AX720's and I was in love with them for a while. I started getting really bad crackles(I tend to listen full blast all the time lol) so I used my warranty to get a new pair. Turned out that they were discontinued so I opted for Turtle Beach PX21's and right off the bat I noticed that they arent as loud as Trittons, but they do sound much much better.
I think Tritton just trys to full people into thinking its quality by just uping the volume of everything. I want to upgrade soon, and the Tritton Warheads look pretty nifty, but $250 is quite a big bite into my wallet lol.
To get back on topic though, I use Turtle Beach PX21's and I love them. They are perfect for games like COD, and even when I play racing games and what everything sounds great. So I would say it is a great mid level head set, and they are cheaper then the same level trittons that I had($110 compared to $130)