I think you are asking what to do for better performance in games.
If you need more graphics power, your PSU should be capable of running a graphics card as good as a GTX660ti or a 7850.
IMAX is not a familiar brand, so I might suspect it's quality. If it is poor, you might want to replace it regardless.
On the cpu side, you have a good duo which could probably be replaced by a quad like a i5-760.
That is of value if your games are multi core capable.
My take is that it is better to completely revamp the total rig instead of pouring money into a partial solution.
If you can't do it all at once, then a better graphics card can help now, and be carried forward to a new motherboard/cpu rebuild.
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.
If your FPS stays the same, you are likely cpu limited.
b) Limit your cpu, either by reducing the OC, or, in windows power management, limit the maximum cpu% to something like 50%.
This will simulate what a lack of cpu power will do.
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.