The cpu probably wouldn't bottleneck it, at least not significantly. A 450w psu may be enough but it depends on the amps on the 12v rails. If you post the model of your psu we can make sure it is enough.
The X2 5000+ can hit 3.0ghz on stock cooling with no voltage increase. Once a CPU hits 3.0ghz it doesn't or barely bottlenecks. Dude just OC you CPU and you won't have to worry about bottle necking. My 4800+ at 2.8ghz wouldn't bottle neck a GTX 280 so you don't have much to worry about.
CPU bottleneck is pretty much determined by the resolution you play at. The smaller the resolution, the less the video card becomes the bottleneck and the more the cpu does.