First of all, welcome to the HTPC club. If you haven't already been there, think about going over to the AVS forums. They have a great
HTPC forum. If you can't find the answer to your question in your searches, they guys over there will be able to help.
It sounds like you have the audio covered. Before you upgrade the card to the Audigy 2, be sure that the integrated doesn't do the trick, especially since you are going to be passing the digital signal to the receiver. I have an old POS card that does this function very well....the receiver is doing the work in that scenario.
As far as HD goes, what is your source material?...Over the Air (OTA)?...Cable? I'm not completely up to date w/ this stuff, but running cable-based HDTV on a HTPC is tricky. Only a few cards support it and none of them will decode the protected HD channels. Both inputs require a card that has an HD tuner on-board. I would suspect that your card will output an HD signal, but doesn't have that tuner on-board. This ability to output HD w/out a tuner would be used more for some of the HD DVD titles out there (Coral Reef, T2, Step Into Liquid, etc), which are decoded, etc via software.
I hope I'm not overwhelming you. There is a lot to cover when dealing with HD on HTPCs. The cards that can do this are all new and are going through continual bug-fixes, etc. In my case, though I will try to screw around w/ it, I will probably use the Comcast box for cable-based material and then used the PC for the movies.
Other things people play around with is ripping DVDs and storing on your hard-drive. This can be storage-intensive, but it can allow you to play around with front-end software that turns your PC into a kind of jukebox.
Oh, almost forgot...HTPCs output progressive scan images, which many take advantage of instead of updating their DVD players.
The list goes on and on. But, for most of us, it is just another fun way to screw around w/ computers. Hope some of this helped. Enjoy!
