Im running a C2D e8500 @ ~ 4.0GHz with a GTX 650Ti and as much the GPU is okay for this game ( not ultra settings though) the core 2 duo just can't keep up. Im getting reasonable frames 40-45 but the game stutters because it's just a dual core. I've seen some pentiums and i3s run the game without stuttering but i wouldn't really cound on that so a quad-core is a MUST, believe me. The specs im rocking now were fueled by an ambition to run new games but investing in old hardware turned out to be a huge no,no. Soon im building a complete new skylake based PC. I suggest you save up some cash if possible and really buy something thoughtful. As for a 775 CPU if you really can't afford to do a new build maybe, but just MAYBE look into the core2quads.