reduce the rez, turn off shadows and blur and put 4x AA and forget about vsync
if that doesnt help, getting a new gfx card, anything over a gtx560 ti or 6870 wont hurt you.
im no reference with my sli 670 tho when it comes to low graphics, im all in and 2560x1600rez, fuck 1080p

my dell 30inch tft ips pannel prolly costed twice as much as your pc