There are motherboards that have built-in sound with DD capabilities. Nvidia Nforce based motherboards spring to mind.
EDIT: Here's a link about the Nforce chipset's audio capabilities. Link
It mentions DD 5.1 encoding, but nothing about DTS. I assume it still has the capability to output a DTS bitstream (?)
Soyo has a P4S (I think the P4I has it too) Dragon that has digital in and out. I haven't gotten the machine built all the way yet, but the reviews on it are great.
Rememmber, those reviewers may not be like us. Sound to them may not be the same to us.
"Supports 4/5/5.1 speakers and DLS based wave table music. Also provides professional SPDIF IN/OUT non-distortion digital interface"
I probably won't use it either as I already have a 5.1 system (SBLive! w/DTT2200) in another computer and got an Audigy for this one that I will end up putting a new speaker set on. Maybe move the older setup upstairs for surround sound when I watch ST:TNG on DVD.
Is Power DVD a software program or a sound card? If it's a software product, would all I need is a sound card that would pass a uninterrupted digital signal? I plan to ultimately use my Pre/Pro to decode my DD/DTS signals. Would I be off track or right on?