At a res of 1440 x 900, would i see any difference with the either the 9600gt or the 8800gt? I dont play many games, mostly 2142, and i'll load a FPS here and there to try out. My CPU is a dual core amd opteron (939) so I'm sure it's a bottleneck.

I have the 9600GT and I run 1440x900..for anything but crysis it has been able to run on high or max settings at decent framerates. I don't know about bf2142 but I run C&C3 at max settings and I hit the 30fps cap.
 
The 8800GT is better but also more expensive. Both cards are approximately the same price/performance so go with whichever matches your budget.

For this resolution, if you wanna save money, you can go ahead and buy the 9600gt

If you look around and are willing to go through the rebate dance you can find 8800GTs for $10-$20 more than 9600GTs
Evga XFX 9600GT 8800GT prices

Anybody know how long the alpha dog edition 8800gt is?I have a dimension e520 and i'm wondering if its gonna fit.