Could you tell us more about your system? MB,RAM,PSU,HDD Monitor. It's possible the MB chipset has Graphics. That's how it was often done back when that was current. You may have a lot of better CPU options available for little money, or a free overclock to 3Ghz.
Also which version of Q6600? SLACR is the good one, SL9UM not so much. Without knowing more i would suggest a GTX1050-2GB and at leat 6GB RAM. The 750Ti and GTX1050 usually don't need a PSU upgrade.