Getting the best GPU without bottleneck

You have a relatively well balanced cpu/gpu combination for gaming at 1080P.
It is not clear to me how much you would benefit by a stronger graphics card unless your games are fast action shooters.
You might benefit more from a cpu change.
Here is my stock approach to that:
Some games are graphics limited like fast action shooters.
Others are cpu core speed limited like strategy, sims, and mmo.
Multiplayer with many participants tend to like many threads.

You need to find out which.
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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 or more cores/threads. 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 threads to less than you have.
This will tell you how sensitive your games are to the benefits of many threads.
If you see little difference, your game does not need all the threads you have.



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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If you decide a graphics card upgrade should come first, then make it a three tier jump or you might be disappointed.
http://www.tomshardware.com/reviews/gpu-hierarchy,4388.html
That would be to a GTX1070. Current amd cards tend to be overclocked and require more power and consequent noise.
To reduce the chance for coil whine, buy a stock card that does not need to work hard.
Also, your psu may not be the most stable, and that can contribute to coil whine.
A graphics card upgrade is simplest, and can be carried forward to a new cpu upgrade.

FX cores are slow, so a cpu upgrade may well be what you need first.
If you decide on a cpu upgrade, look to more modern kaby lake or ryzen processors.
If you heed fast single thread performance, look at kaby lake.
If you need more threads, ryzen is hard to beat.
In either case, you are also looking at a new motherboard and DDR4 ram.

If you de