Eh what he means is if you are running stereo which is 2.1 or headphones, a sound card doesn't matter much. Only if you want digital surround sound which only works ok for games and things like movies that are encoded in 5.1.
You should be fine with using your receiver as a sound card. I would use you optical sound out of your mobo though.
You should be fine with using your receiver as a sound card. I would use you optical sound out of your mobo though.