No need to go for the fastest cpu, anything 3Ghz or over will do. Put 1Gb of memory in it (at least pc3200).
For graphics dont get an ATI 9800Pro, There's a much better card around, at least hear in the uk, the Nvidia 6800 LE, it about the same price and is a LOT better.
If your budget allows, get the 6800GT, the Ultra is a little quicker but is too expensive for the speed increase gained. That money could go on getting a raid array. Also the GT, if your lucky, will overclock past Ultra speeds anyway.
Cpu choice, if your just going to play games, an AMD will be fine. If you plan to run many apps, then an Intel is definately the way to go.
Intel Core2Duo 6400 @ 3.4Ghz
4GB Geil 6400 Ultra
3 x 500 Gb Samsung HD
EVGA 8800 Ultra OC