Here are some tests you can do to help decide:
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To help clarify your CPU/GPU 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 more cpu limited.
b) Limit your cpu, either by reducing the OC, or, in windows power management, limit the maximum cpu% to something like 70%.
Go to control panel/power options/change plan settings/change advanced power settings/processor power management/maximum processor state/
This will simulate what a lack of cpu power will do.
Conversely what a 30% improvement in core speed might do.
You should also experiment with removing one core. You can do this in the windows msconfig boot advanced options option.
You will need to reboot for the change to take effect. Set the number of processors to less than you have.
This will tell you how sensitive your games are to the benefits of many cores.
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.
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Individual core speed of FX-8320 will be similar; you just get two more.
If your games are not well threaded, expect no improvement.
And... just because you see task manager show activity on all threads, and less than 100% usage, that does not mean you are using them well.
It is just windows spreading out the activity of a few threads.
If you decide graphics, GTX1060 is just two tiers higher than a GTX770.
You may be disappointed if you do not see big results.
Still, GTX1060 is about right for 1080P fast action games.