Alright, I did some research on this one. You can use this with a PC/PS3, but you need adapters. Here is the manufacturer's part's page, go here to buy the adapters I am going to mention. May be available cheaper elsewhere, but you're on your own for that.
For use with PS3 - Buy the PS3/PC Chat Adapter Cable + Amigo II (The $30 one). YOU NEED THE AMIGO II FOR THE PS3. This kit will also allow you to use your headset with a PC.
If you don't have a PS3 and just want to use it with a PC, buy the PC Chat Adapter Cable ONLY. ($10) You don't need the Amigo II for PC.
Potentially helpful illustration that Turtle Beach provided for hooking up a 360
Side note on the Amigo thing, it's basically a USB sound card that a PS3 recognizes.
If you want to upgrade your x31 to a sort-of x41 buy the Ear Force DSS. It converts a digital surround sound signal into an analog stereo one usable by the x31 or other stereo only headsets. If you don't know what this is, you probably won't notice the difference.
Additionally, please note that the X31's don't use optical/digital signals like the x41's, they use a standard 3.5mm jack (Think headphones) as an input but come with RCA passthrough cables (the red/yellow/white cables on almost everything). You may need to use some trickery if you use HDMI to connect to your TV, I haven't tested it as I do not have the headset yet. Wish I had jumped on the x41's personally, but these will do for me. I'll try to update this if I find anything else useful. Also, first woot for me after lurking for a while wooooooooooo
EDIT: clarified some things, corrected spelling