9800 GTX, E8400, 2 gigs, maybe even 4 gigs of RAM (if you want to run Vista, get 4 gigs and 64 bit Vista, unless it doesn't really matter, but RAM is very cheap), DDR2 naturally, DDR3 is just not worth it, a 500 gig HD (or two of them if you need the space), if you need 'more' HDs (but not more space), just partition the hell out of it, a good PSU (i am generally looking at Tagans which are very nice PSUs, dead silent and not that expensive here, i'd look at some Corsairs or Enermaxes (but Es are expensive, Corsairs are very good for the price), a nice case (Antec P182 for example) and a Scythe Mugen for example over the CPU. Some other may be nice too but i don't really know much about air cooling since most of my buying research is based on water cooling lately.

As for the mobo, P35, it's a 'must', you could go for X38 but it supports crossfire (which you don't want) and DDR2 performance is generally slower than on P35. So P5K series as i've said (in this topic?), Abit IP35-PRO, maybe some DFIs if you can get them. As for the P5K- take a look at the P5K-E, P5K-PRO or P5K Premium. I wouldn't go for DDR2/3 mobos, they generally aren't as good, well they are good on both fronts but no excelent. SO no P5KC in my oppinion.