well what do you have now?
whats your budget?
whats your main use?
which country do you live in?
have you got any specialist secondary uses (e.g. CAD, media editing)?
You will need 2gb of ddr2 ram and most people get 6400
A 8800gts 320mb will be better then 2x8600GT (sli gives you a 30-40% performance increase for 100% of cost)
BTW You cannot use PC4300 RAM with the P965 chipset you must use DDR 2 RAM. Upgrade 2 would be better but get e4300 and OC it, 2gigz of PC2 6400, X1950XT or X1950PRO they will both kill the 8600 for a cheaper price and P35 chippset mobo, preferably the Gigabyte P35 DS3-R.
I ended up going with a Core 2 E6320, Abit IB9 (P965 Chipset) and just added 512MB to my exsisting 1GB DDR2 533MHz RAM. The video card well i got it for free a gigabyte 256MB GDDR3 8600GT OC'd.
I managed to get an overclock on the processor from 1.86GHz to 2.10GHz but my RAM kept me from going any higher.