is your mobo a sli? if so get at least 600w power supply and I would definatly get geforce 7800 gt or gtx for your GPU and definaly go with corsair xms 2-2-2-5 latency ram at least 1.5 gig preferably 2 gig if you plan on playin BF2,Quake 4, HL2, Doom 3 and so on especially these games if you play on ultra quality they use 512 ram just for added textuing alone so 2 gigs is a must for smooth gameplay on highest graffix settings.
here is my setup:
Fatality a8n sli
amd 4000+ 1 meg cache
2 gig xms corsair 2-2-2-5 latency
2 bfg geforce 7800 gt oc
600w power supply
maddog cd+dvd burner
HD WD sata 120gb 8meg cache
xp pro sp2
hopefully this is helpfull to you and anymore questions feel free to ask!
Craig