I have the X-fi, it has optical, but from what i understand, ifyour planning on gaming in surround, your going to have to use 3 analog lines to run a mock 5.1 system, due to the fact many video games arent encoded in THX/Dolby etc, most are EAX, making it impossible for your reciever to decode
I havent hooked my comp up to my systems yet, i have a HK AVR 145 reciever, ill post again, once ive dug deep into the sound card side of it