Well, for CS5, you might want an GTX470/480 for the CUDA support.
Overkill. Your better off with an "old" 9800GTX,etc. The performance gain over a 9800GTX with a GTX470 are minimal for CUDA enabled features such as zoom,etc. Same goes for vid play back with Mercury (assuming nothing insane is being done, ie high end pro level work).
You probably want:
ASUS P6T SE
Intel X28-M G2 80GB for OS + CS
Corsair 650TX or other quality PSU from XFX, Seasonic, Antec, Corsair, PC Power & Cooling.
3*2GB DDR3 1600 or 6*2GB DDR3 1600 from GSkill,Corsair,etc. I recommend the GSkill Ripjaws. 6GB vs 12GB depends on work load,etc
2x 500GB or 1TB Samsung F3s for data/storage
nVidia GTX260 or even a 9800GTX (can be had for <$100 now)
Windows 7 Home Premium x64
Btw, go DIY. Screw Cyberpower.