Well... You would be a whole lot better off by replacing the GPU and PSU, but the 2.33GHz CPU clock speed would still be holding you back (assuming you can't overclock). The good part of your proposed upgrade is that the GPU and PSU could be used in a future build and not a "waste upgrading an LGA775 system". Stick wtih XFX, Antec, Corsair or Seasonic for a good quality PSU... 550W is fine, but a "safe" recommendation would be a 650w PSU for a single GPU, or 850w for dual GPUs on a good gaming rig.
Sweet, thanks a lot guys. Am i missing anything as far as components go, i only have a small window of time while im in the states to build this thing. i would like to have everything ordered before i land.