Updating my old graphics card

[Tyrael160]

I have and older system that i need to upgrade while i save up for my new build, the old system will then be given to my GF.

It has an EVGA 780i FTW mobo, I forget the CPU i know it is a socket 775 quad core running sightly overclocked at 3.4GHz, and 8 Gb of ram, and a 1000W PSU. Current graphics cards are twin EVGA 9800GT in SLI

I'd like to upgrade my graphics card but i don't want to waste money on something like 700 series that won't be fully utilized. What's the best card I can use for the money?

 

[Onus]

A HD7790 or R7 260X would be decent without spending a lot of money, or perhaps a GTX660 if you want to stay with nVidia.