Need recommendation on video card upgrade

Hello readers,
I have an older Athlon 4000+ SLI system with 2xGeForce 7600GTs
I primarily use this PC to game and want to upgrade the cards. The system is probably too old to warrant putting in 2 high end cards so what would you recommend short of buying a new system?

I need help deciding to either purchase a new, single ATI 4670. Or I could stick with Nvidia and get a maybe get a used 8800GT. How much would you pay for an EVGA 8800GTS 640mb. There is one on craigslist locally asking for US $100.00.

Sorry for the discombobulation of thoughts and questions. Budget is $150.00 max. Looking for cheapest workable solution to run FarCry 2.

Thanks!

The 9800GT will put some spark back into that old AMD rig.
I am running a 4600X2 clocked to 2.8ghz with an 8800GTS 512meg G92, and though I know it is no match against the newer CPU's, it gets the job done nicely for me. Scores just over 10,000 in 3D Mark 06. Would be huge gain against the 7600's you have now.
Check the GPU charts on the main page of Tom's to see what games you play and check the scores between the cards.
Forget about the 8800 320meg GTS, it is just too old for the price. At least buy a card with the Nvidia G92 chip, or an ATI 4800 series. There are several 4850's on Newegg for under $150 if you want to spend that much. For the money though, that 9800 looks pretty good.

Thanks guys. I'm going to stick with Nvidia and pickup a 9800GT single slot or 9600GT. Not much difference in price after rebate so probably go with a 9800GT from the egg. Now what to do with those 7600GTs

fcuk rebates man, I got screwed on one of newegg's rebate partners (rebatecenter.com or something) who claimed i never sent them anything.

is that dual core 4000+ or single?
If it's single your cpu is probably already bottle-necking the 9600gt and sli would be pointless.

my existing CPU is a Socket 939 Athlon64 "San Diego" core with 1mb L2.
I bought the 9600GT, figured that would be a fine upgrade from 2xSLI'd 7600GT. After I ordered I found a $30.00 rebate so it'll cost around $75.00.
I'm sure I'll be happy with it. I'll post back with how it does with my aging system. It's funny cause I could still run new games just a lower settings, now I hope to bump it up/smoother. I play at 1680x1050. I found using tweakguides helps a lot.