I'm not an expert on this, but here's my experience:
Have ATi AIW & SB Audigy; I then removed both to install into a new computer (with new HD). I install the ATi first including the software to run the TV tuner (which maybe a mistake -- to install the TV tuning capability, since I think this particular feature demands a sound card). When I booted up, ATi message says can't detect sound card (not yet installed) then locks up the PC at various stages; sometimes I can't even boot up the system. Fortunately it was a brand new hard drive so I just reformatted to get rid of the ATi stuff. If I remember correctly, I think I also tried to reinstall with just the ATi driver, without the TV tuner, and had the same problem. It was not a fun day. Don't think I can help you much here cuz ended up using the old hard drive with the ATi & SB Audigy already on it. I think it does need a sound card, although it can output DD directly (although I believe it needs some tweaking with DVDgenie)
