What performs better @1680x1050 9600gt SLI vs 8800GTSLI

Which SLI set up performs better, the 9600gt in SLI or the 8800GTS in SLI?

I am building a gaming pc, so far I have a q6700, 74 gb raptor hdd and 2gigs ddr2 800 444-12. I am thiking about getting a ASUS P5N-D SLI and 2 gigs of ddr2 1200 to oc it to 3.6ghz to 4ghz.

I am trying to keep the cost down, if anyone knows a of a better motherboard in the 100 to $150 range let me know.

current setup:

Q6700
P5B Deluxe
2GB DDR2 800 4-4-4-12
6800GT
74gb Raptor