jackschmidt, I'm glad you found us, but for what you're describing, LinuxMCE might be overkill. LMCE would be for a situation where you say, want the tv to automatically turn on, lights dim, etc when you put in a movie, or be able to control security cameras and lights with your tv remote. If you're just interested in building a DVR/computer-over-tv, I'd look into MythBuntu or something similar. If you are interested in doing more than just tv, then I would look through the wiki, specifically: http://wiki.linuxmce.org/index.php/Hardware
You'll want a hybrid (one computer) system and will use something like a HDHomerun or one of the other devices here: http://wiki.linuxmce.org/index.php/Category:TV_Cards
to input the signal into the system. As far as computer to tv, any decent video card with dvi or hdmi out will be able to run a signal to your hdtv. Again, just look through the wiki and forum and you'll find specific examples people have given.