I would definitely get a 450w fortron or better. You are not bottlenecked by GPU or CPU at all. The GPU is the most important factor in your gaming experience. You wouldn't feel the bottleneck unless you were running something like a celeron or other super-budget-class CPU(which you're not).
Important factors in gaming from most important to least important:
1. Stability of PSU and Motherboard(because if that's not stable, even having 4 Radeon X1900XTXs in Quad-Crossfire(not out yet) would do you much good.)
2. GPU horsepower. This will determine how much settings you can enable for a game. My personal acceptance level is 1024*768 with 8xAF(it doesn't impact performance, at least, not noticibly) and medium settings because you're not going to be staring at the little holes in a brick wall when the enemy is shooting at you in the game. Generally, High end GPUs(Like the 7800GT or X1900XT) get you 2-3.5 years of performance. Mid-Range GPUS(like the 6800GS and 7600GT today) get you 1-2 years of performance depending on the model. Budget-Midrange(like the 6600GT today) GPUs get you 0.5-1 year of performance. Anything less(I'm talking like Geforce FX 5200s and X300s and X600s and stuff like that) and you should save up for something better. The GPU determines the majority of your performance.
3. Amount of Ram- Just the amount. Ram is important because it determines load times and determines if you'll get stutters or not. This is just a notch below GPUs in importance for gaming experience. I remember when I had 512mb of ram and a EVGA Geforce 6800(the non-ultra, vanilla 12-pipe version) 128mb, which was a pretty high end card in December of 2004. I played Far Cry with it and it stuttered like HELL on 1024*768 resolution with 2xAA and 4xAF. I know it was the ram because Guru3d had it going good at 1280*1024 with a Gig of ram. Today, I recommend 2 gigs of ram for smooth experience, unless you like stuttering.
4. CPU- The least important factor in gaming. You should not be worried about the CPU unless you have something like a Celeron or other super-budget-class CPU. Even then, you could still get a smooth gaming experience with a high end GPU.