Honestly, the 8800GT is basically THE best GPU price/performance wise at the moment. If you can afford it, I would definitely pick one up.
AMD Athlon 64 X2 5200+ is generally better price/performance than the X2 6000 (roughly 40~% price increase for 10~% performance increase) as far as CPUs go.
Also, do check how generic RAM compares to the 'Crucial' brand price wise. I have always used generic RAM and have never had a problem. (Every benchmark I've ever seen only shows 'high performance' RAM beating generic by 2 - 3~% at most.)
Beside that however, if you can afford the parts you've already listed, I'd say go for it. Would be a top machine.