if you are interested, here's my thread on my Crysis 3 benchmark, where I saw a HUGE CPU bottle neck, just to give you an idea of what to expect:
http://www.tomshardware.com/forum/395367-33-crysis-benchmark-560ti
LinusTechTips also has a GREAT video on you tube about CPU bottlenecks, where he takes a GTX660 and hooks it up to the Core 2 Duo, not unlike yours, and its pretty incredible
while certain games are much more prone to CPU bottlenecking, like StarCraft 2 and Skyrim, its really your low playing resolution of 1366x768 that forces the bottle neck. its just doesn't ask the GPU to do enough graphically so the work falls to the CPU instead.
Notice in my thread, at 1280x720 on low settings, my average frame rate is 41 with i3 and 65 with the i7. thats a 50% increase in performance, just swapping in a faster CPU. now, if you look at the 1080p performance, the difference is only about 10-15% increase in performance going from the i3 to i7. its because 1080 is more graphically demanding than 720
Happy hunting! Let me know if you get it!
Dry