I built up a Home Theater PC last year based on the Intel Pentium M, the ATI 9600 with component output and a home theater case with 60GB of memory. I actually got it to boot up in 1080i mode although I needed a dedicated LCD monitor and I also found the ATI software to be really unreliable in driving the 1080 display. Plus, I had a IR keyboard and mouse that just didn't work from 15 feet away, so the whole thing has been sitting in the corner as a hot standby for when a PC crashes.
Well, never one to give up, I'm going to see what the state of home theater is now. With a DCT-6812 box and a Panasonic X30 plugged into a now old (7 years!) Mitsubishi 73905 rear projection TV, I'm actually quite happy. I don't know what I'll do when I really have to go to 1080p and the new step, where this 400 pound monster will have to go somewhere (you can't just throw that in the garbage!).
In the mean time, its interesting to see where HTPC technology has gone. A quick google:"HTPC" reviews that there are quite a few old sites like "AVS Forum":http://www.avsforum.com/avs-vb/forumdisplay.php?s&forumid=26 as well as new sites like "HTPCNews":http://htpcnews.com and "HTPCForums":http://htpcforums that are dedicated to just building them. Here's an update on what's available: