Core 2 Duos aren't going to be outdated anytime soon. If you want, you could buy a $180 1.86Ghz E6300 and overclock it to over 3Ghz, and you would have something that has absolutely no competition right now. Even AMD's competition to the Core 2 Duo is still a good 8-10 months away, so that's a "guaranteed" time of non-outdatedness, lol. 2.4Ghz is obviously better, but you should invest the money in other things, like a better videocard.
Speaking of which; there is no way you're going to fit a $630 8800GTX into a $1000 budget with a $180 processor and $200+ of memory.
If you want, just give us the go-ahead and we'll design you a $1000 computer. You live in the US, right?