GPU vs CPU Final Decision

I would upgrade the GPU to something like the GTX 950 you've listed, there's a little bottleneck in CPU intensive games, but definitely an increase in performance. As it stands right now, even with the upgrade to an FX-6300, you wouldn't see the same performance as your friend with the i5-3470, the difference between the two is pretty big, as is with the 6300 to your X3 455.

If you plan on playing GPU intensive games, go for the GPU, vice-versa with the CPU. If your MOBO and CPU are good on overclocking, you can overclock to see some (small) gain in performance.

No other way around this: get a new GPU when you can also afford a new platform(dont put any more money in that dead am3 platform!).
These days i would say get an i3 6100 and an RX 470 when it's out.

That CPU is rubbish, I mean with my dual core G3220, I can get better performance, even if your CPU is triple core.
Because my CPU has a 50% stronger core than yours, so I suggest you get a motherboard and CPU from intel's side.
Doesn't have to be 6th gen, if you don't have money for new ram, 4th gen will do just fine, and i3-4160 will do just fine, it will perform close to an i3-6100, which is very good.
After that your bottleneck is the GPU, getting an RX480 for $200, you get the performance of a GTX 980.

Much depends on the types of games you play.
Strategy games, sims, and mmo tend to be dependent on the performance of the single master core.
Your X3-455 has a single passmark rating of 1138.
AMD processors have relatively slow cores. FX-6300, for example is 1408 most others are in the 1500 range.
Since most games can use only 2-3 cores, 6 and 8 core processors are not optimal for gaming.
Your friends i5-3470 has a single thread passmark rating of 1908.

By comparison, the very cheapest Intel skylake G4400 dual core is 1869.
If you are looking for a mid range cpu upgrade, you can do very well with a Intel i3-6100, single core rating is 2102.
You are looking at a motherboard and ram change.

If your games are fast action shooters, then the graphics card becomes more important.
GTX950 or R7-370 would be a appropriate upgrade.

Here is how to tell if you are cpu limited or graphics limited.
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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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