In your case it is unlikely that increasing RAM would improve performance. Keep in mind that Windows would use a swap file when it is short of memory and the only way performance could improve would be reduction of excessive swapping. From your information you don't have any swapping going on.
In some applications it could make a difference (like PhotoShop when manipulating huge pictures). In most applications it would make no difference at all. In 3D it is likely that the processor speed would be a far greater bottleneck than a shortage of memory.
I do assume you have overclocked your i7 processor to reasonable levels (they can all be overclocked quite a bit). Pay attention to cooling.

Increasing RAM is spending money that could be spend better on improved cooling (and thus further overclocking your processor).