Sounds like a really neat project!
ok personaly i have no idea about what software to use but if you figure it out i would love to know. I have a direct tv tivo unit and im unhappy with it. would be great to have a pc to do it so i could just stack in a few hard drives to get alot more record time. not to mention dvd burning happyness from stuff i recorded.
As far as a sound card goes... it really depends what exactly you want it for. Do you plan to hook up surround speakers from it? Basicly anything you would want it to do should be possable with a basic soundblaster card.
http://www.newegg.com/Product/Produc...82E16829102004
Thats a nice one under $100 7.1 surround should be plenty for the sound system media deal your going for.
http://www.newegg.com/Product/Produc...ve&srchInDesc=
Any of those should be good if you want 7.1 surround speakers. I have a older set of the 5.1 creative surround speakers that i really love. Think they are only 45 watts but they are loud enough to shake the house and piss off the neighbors if i wanted to. never had to turn up the volume more then 25% of the way. Basicly creative labs speakers are good quality for cheap price and well worth it. They are very deceptive looking though. very small for the sound they make.
Ok just gonna go back to drooling about the idea of having 750gig or so of storage for a tivo with a built in dvd burner for it. yeah i really want to know how this project turns out for you.
Someone just told me that they have heard of a linux distro thats ment just for this. Basicly turn a computer into a tivo unit. he didnt remember what it was called but it might be worth looking for on google.