The Audigy 2 does Dolby Digital EX (6.1). The Audigy does not to my knowledge. I have an Audigy presently. It takes a stereo sound and mixes it to all five channels, but I'm not sure which format it uses to do it. I did not see DTS listed anywhere, but Audigy 2 will do DVD-Audio. Now someone needs to make a drive that can read it.

I have looked more at both the Extigy and Stereo-Link. Both of them look good. I like the Extigy a little more because of it's features and it can handle more channels. The Stereo-Link only does 2 channel, not too good if you want DVD. I still wonder if something like an SBLive 5.1 with the input/output bracket would work well. This would give a digital connection. I don't know if it decodes Dolby Digital 5.1 though. That's the bad part with the Extigy, in that it can't do it with the optical cable either.