8800gts performance

i got a 7900gt 256mb, amd 3800+ 64 singlecore, 2 gigs of ddr1

will I get any performance increase if I replace the 7900 with a 8800gts320 mb?

Im not planning on playing any dx10 games on this setup, only dx9.

I dont need the most at the moment, just enough to play the newest dx9 games on high in maybe 1600x1200 noAA.

Im upgrading my whole rig later this year so I thought I could get the gpu first and play my dx9 games smooth

ok if I get a new mobo,powersupply,ram,and a core 2 q6600 will I get a performance increase from my 7900gt?storjohan_