In game audio and chat on USB Headset

[NeoMagic33]

hi folks

was wondering how do i go about getting game audio and chat funactioanlity on my usb headset.

I was looking at this Turtle Beach Ear Force PX21 - How Does It Work?
but its around £70 for me to get one, dont wana shell out that money especially after buying the USB ones i already have.

SO question is how do i do it and is it possible to buy the Inline-amplifier and audio splitters shown on the picture?

thanks