Health Nut:
I appreciate your confusion. Quick question re your intentions: do you have any need or reason to want ANALOG sound out of your PC?
If so, then I suggest that you keep the M-Audio card and find a way to use Girder (in conjunction with ML/DVDLobby) to change your audio settings when you switch from digital out (TT, MyHD) to analog out (MC9, whatever). In other words, use your motherboard spdif output for all digital sources, but use the M-Audio card for all analog outputs.
If you have no intention of ever using analog outputs from your HTPC, then I'd return the M-Audio card and use your motherboard's sound for digital out.
Like Axel, I have had just too many problems with TT and MyHD and my M-Audio Delta 410 card. I intend to pull my HTPC out of its rack tomorrow and install the SPDIF output for my motherboard and use it exclusively for TT and MyHD. I'll leave the Delta card in place, however, for multichannel ANALOG playback, and just use Girder to switch outputs when necessary.
- Ken