Sounds OK. If you want to use it with the rest of your home entertainment stuff I would recommend getting a decent fan like a Coolermaster Jet7 and turn it onto silent mode to keep it all nice and quiet ;)
A CPU upgrade would also be useful but not necessary, especially if you aren't gonna be doing much editing. If you do get the personal cinema thing go for the 5900 series as the others are underpowered.
Furthermore, maek sure you do a clean format and installation of XP once you have all the bits together to get the best performance out your system, you won't want it crashing every time you want to record something.