Let's talk Home Theater PCs

Hey guys. Anyone have or interested in home theater PCs? I've never built one myself, but it's something I've been thinking about. However, I don't know that it's entirely necessary for me so I'm wondering what uses people put them to. Just movies and music?

The other thing is, as far as building one, what sort of parts do you go for? I was thinking an ITX board or mATX at most inside a small case, so that it's not much bigger than a gaming console or home theater receiver.

I bring this up because I have a PS3, which I use to stream movies off my PC. The problem though is that it doesn't reconize many movies/formats and also has a size limit so 1080p movies generally don't work. On top of that it's really bad for streaming music, the only real option is to upload all the songs onto the PS3 itself and then form playlists but it's just a pain in the butt. It also won't play podcasts. I wish I could try installing Linux on it and then use the PS3 for an HTPC but... obviously Sony nixed that idea.

I wouldn't want to spend much on it, and it's probably a future project. Unfortunately I just brought my girlfriend's old 1.8ghz dual core and mobo to the recycling depot so I'd basically have to start from scratch. I'd probably run Linux on it, as I don't want to spend another $100 on another Windows 7.

Also, I'm curious what video cards and/or sound cards people use for them? What specs do you think is necessary?
 
I would wait for a couple of weeks for the Llano desktop CPUs. Typically you use a HTPC with a TV for watching movies, recording stuff from your TV with an adequate TV tuner/recorder. You can also make a HTPC/gaming rig.