What about RAM? I have 16Gb's and some times it can use the whole lot...
Ensure you Ram is in dual channel config?
If this still doent help then buy a new card, dual 5750's will use to much power and heat your system to much for the output thell provide, buy a new card
Or crossfire with a 6770 - apparently it works according to AMD. Be more power than another 5750
Its what i plan to do with my 5770, but im only upgrading because i like to game too
Intel Core i5 2500K /-\ 32Gb 1600mhz RAM /-\ Asus P8Z68/GEN 3
2x 256Gb Crucial M4 /-\ Crossfire XFX HD Radeon 7950 Black DD
Sound blaster Z /-\ yourpcperfect.com /-\ Windows 7 Pro