I went from 6GB to 12GB, and aside from allowing me to run more Virtual Machines at a time when testing and noticing less severe framerate drops when maxing out my VRAM in Surround resolutions, I didn't see a great deal of difference. Given you're already running 2GB cards the VRAM limitation isn't a serious issue, and you're only running a single monitor so you likely won't notice much difference at all.
