I suspect you have a reasonably well balanced system.
It is not clear to me if a cpu upgrade would do you more good than a graphics upgrade.
To help clarify your options, run these two tests:
a) Run your games, but lower your resolution and eye candy.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
b) Limit your cpu, either by reducing the OC, or, in windows power management, limit the maximum cpu% to something like 50%.
Go to control panel/power options/change plan settings/change advanced power settings/processor power management/maximum processor state/
set to 50% and see how you do.
If your FPS drops significantly, it is an indicator that your cpu is the limiting factor, and a cpu upgrade is in order.
It is possible that both tests are positive, indicating that you have a well balanced system, and both cpu and gpu need to be upgraded to get better gaming FPS.
If you used different speed ram, you will default to the lower speed. As long as all the ram is working ok, I do not see that as a big deal.
I don't think I would spend more on a system that ie a few generations old.
But... you seem to have the itch. Consider saving up and scratching it.