overclock your cpu & gpu it`s free
the q6600 at stock clocks is kinda slow, you need to get it to at least 3ghz to play gta5 or far cry4 smoothly,
10-15% of overclock on gpu clock $ memory will do it,
I have a q8400 at 3.2ghz and r9 270x overclocked 15% (almost the same build as yours)
and i can play gta5&far cry4 on 40+fps at 1680*1050 with high settings except for the shadow quality, postFX and particle on medium
you might need msi afterburn to cap the fps at 35-40-45,
With vertical sync the fps fluctuate a lot between 20-60, it can make the game stutter
tldr a core2quad with frequency lower than 3ghz will be a bottleneck
at 3.2ghz it`s on par with an i3 4130