You'll need A/B switch, adaptor converted cables.http://www.amazon.com/RCA-VH915-Source-Selector-Switch/dp/B00008X5DF/ref=sr_1_71?s=electronics&ie=UTF8&qid=1287808680&sr=1-71
Connect this between PC and A/B selector/switch - http://www.audiogear.com/cgi-bin/shopper.cgi?key=Adpt2RcmMsm2M&preadd=action
connect xbox RCA Audio to selector B
You should have the cabling of the picture below for the next one to work. http://forum.teamxbox.com/showthread.php?t=613147
- you must have the RCA that needs to connect between the TV and headset that is to be connected to A/B switch and headphone controller instead.
Next is to connect this over the extension port of A/B output http://www.audiogear.com/cgi-bin/shopper.cgi?key=Adpt2RcmMsf10FT&preadd=action
between rca out the speakers.