My mobo has HD 6-channel support... My XB-360 is using the optical input.
Well, I have a $25 motherboard (or close to it; got a combo of a quad w/ mobo for ~$85!) so, hehe, doesn't really bother me; Sound Blaster Audigy 2 ZS recently died so, I've been just waiting until this mobo gives out, to get a... decent motherboard.