my PC for MEA

It seems to be twice slower than my i7-4960X and I had GTX 970OC that couldnt run it with all the bells and whistles set on ultra 60fps at 1920x1200 - so I'd say if you update your GPU only, your CPU is a bit on the way of the performance. Then next thing: you'll gonna run out of memory with only 8GB -> slower perf.

I am not sure, it depends on your motherboard. You may want to see from the manufacturers website what CPU's it supports.

Faster GPU needs also faster CPU to feed it, thats why I think the old 4100 isnt maybe enough. Faster GPU is always going to make more difference also than just faster CPU.

The CPU you have can easily be overclocked to roughly 4.5 and will out perform the Fx-8350 at that speed. No game will use the full 8 cores of that cpu so it's wasted unless you use other programs that fully utilize those cores. Plus your just adding more heat to the whole setup. You don't need 16 gigs of memory as another poster said. 8 is more than enough for MEA. The only time you may use more is if you heavily mod games like Skyrim. The main thing holding you back is your 960 graphics card. Even if you overclock it it still won't be enough. Your motherboard allows for overclocking (It's unlocked) and so does your cpu. Start there and get a better graphics card. 

I've been building computers for the better part of 20 years now from mild to full blown custom water cooled tri-card setups. 

8GB may be enough if you shut down browsers and stuff from background, I do not.
Also overclocking is always a bad idea, never know how it'll go out, wasting time to stability test... I was there, when I was 20 years "stupider" nowadays I'm not bothering with it.

Also "4100 isnt maybe enough" is if one updates GPU on it, the CPU will be the dragging part then. You can see this in many tests when used low end CPU and high(er) end GPU.

I've been building computesr over 30 years now

I guessed right, do say I'm a kid now?

You can do overclocking, I wont. I wont discuss more of this.