Hello Spiffnme,
As for the audio, I have the M-Audio Revolution 7.1. It has SPDIF Coax out, I use it all the time to pipe my vast music collection sitting on my HD to my pre-amp using a 75 Ohm coax cable connected to the AUX port. Works like a charm. Althought the X-Fi is, in MHO, the fist CL audio card that approaches the quality of the M-Audio, I think the Revo is still a better card if you don't intend on doing a lot of gaming ie: 4.1 / 5.1 on your PC. The Revo plays games just fine but does not support as well the proprietary CL EAX . I have used every imaginable CL audio card since the very first one and I find the Revo to be superior, only the X-Fi comes close.
as for some of your other components, the Seasonic is a great PSU, I am running the S12 600W in my new pc now. I am of the AMD camp as opposed to Intel so I am running the Athlon 64 Dual Core 4400+ cpu on the Nvidia Nforce 570 chipset. Solid combination. I switched to AMD back in the very first Athlons and I have not looked back ever since. Although Intel is more on par with their prices recently, there was a time where Intel was significantly more expensive for less performance than AMD..Just my preference, AMD for CPU, Nforce for chipset and ATI Radeon for vid card.
Cheers,
Stephane