GPU Get one ATI X1950 PRO or ATI X1950 XT, they cost like a 8600 GT and has a superior performance...
And try to get some good PSU, with at least 20 Amp in the 12Volts Rails (This is critical is you are going to buy a good GPU and yuo are going to play with it)... Dont follow just the Wattage...
CPU... well I prefer AMD, is cheaper, but if you have the gutts, buy a cheap C2D and overclok it...