Core 2 Quads are dated, I myself am using a Q8400 overclocked machine, it served me well in the first era of the "new gen games", even holds up rather well on The Witcher 3, but it will bottleneck even a GTX 750 Ti on the upcoming games and current new games and even the performance on Windows, do all you can to get at least an i5 4th gen or even the new Skylake i3 6100, which is what I am aiming for right now, my GTX 950 simply cant run the new games due to the massive CPU limitation I have, even with the overclock.
You will not get much improvement, you could get a lot of improvement if you OC your C2Q to 4.00 GHz and beyond, but that requires custom cooling, a very capable and expensive 775, hard to find and most of the time, used mobo and a powerful PSU, not worth the hassle imo, just get a newer gen CPU, any 4th gen i3 or i5 is better than all C2Qs out there and you can throw even a GTX 980 at them and there wont be any bottleneck or very, very small at some games. Dont forget to add 8GB of RAM too. Good luck.