I read thru some of the posts, but not all, but, has anyone asked what it is exactly you'll be using the computer for? Because, if you're just going to be playing live for speed, you can grab a gig of ram and a gpu for around 150$ that will run LFS over 100FPS at all times, with graphics maxed out.
However, if you want to play newer games(Crysis, Quake Wars, COD4), I'd take everyone's advice, as it seems you are, and wait, build a new PC. Upgrading what you have will end up with you spending double the money for half the performance boost.
Anyways, I like what you choose to build.