I've been knocking around the HTPC for some time now. I've read all I can, researched until my fingers hurt... my conclusion... it's not worth the hassle at this point. Until you can have better software integration where you don't have to run this program to do this, tinker with that one to do that, and play around with this to get that going, it just seems like too much hassle... for the time being. I think another year will go by and we'll see a lot of maturity.
For now, I'm using the home media gallery in my 94 to access my music. it works perfect and is all I need for the timebeing. If you do want to connect up, there's several good boards that have HDMI connections. If you can keep it simple, it should be a huge deal, but if you want PVR, Blu-Ray, and all that, it'll be a lesson in frustration unless you have a really deep deep understanding of the stuff... a lot of time... and a lot of patience.
My I.T. guy just went through this. He was having constant audio dropouts only to find after 2 weeks that there was a manual edit he needed to make in the registry. He only found out because he ran into someone over the HTPC section at AVS, but he first had to read through about 27 thousand pages before he found an answer.