Cool, atleast he wouldn't need to change boards then. But i still do stick with what i said to at the very least consider a new system. That series of upgrades will cost a fair amount of money, and i'm not one for putting lots of money into a system for upgrades.
However, thats my personal preferance and i think i've made that clear. To save this from getting out of hand, i'll just drop that point and get to the question on hand.
That 8600 is a good choice. It will run any current game at max settings and the DX 10 support will be nice for the future. May i reccomend an EVGA card? Their service is great, and nothing beats a life-time warranty.
Do you know if your motherboard accepts DDR2-800 (PC 6400)? If it does for i think ten bucks more you could get faster RAM and really see a decent performanc boost (if not used in conjuction with your old RAM as taht will slow it down if it is not the same speed).