I have a ASUS Xonar DG sound card, and currently, I have it connected with my receiver via a SPDIF cable.

The only way for me to have proper surround sound support, is if the game or media I'm playing supports Dolby Digital.

I explained how audio works in this thread http://us.battle.net/d3/en/forum/topic/4838103820?page=1#12 but I guess I would have better results in the Tech Support forums.