The overclocking would have an importance in the framerate. Ambient Occlusion is the top feature under "manage 3d settings." It's only available with the latest drivers so if it isn't there, don't sweat it. The 12GB shouldn't make any difference since this game probably uses less than 2GB. It's nice to have for serious multitasking and many non-gaming programs but unfortunately games just aren't really using more than 2GB of RAM and probably won't for a very long time seeing how most people are running 32-bit OS's.