Single thread performance is what is most important for the gamer.
X4-860K has a single thread passmark rating in the 1500 range.
That is exactly the same as FX-6xxx and FX8xxx.
Most games can only use 2-3 threads so 6 and 8 threads do not help much.
You have no good processor upgrades.
If your motherboard is a good one, you can do better with some overclocking, but that is about it.
Today, intel skylake is tops.
A i3-6100 based upgrade will do you some good.
Here is a review;
http://www.anandtech.com/show/10543/the-skylake-core-i3-51w-cpu-review-i3-6320-6300-6100-tested
If you are an AMD fan, and your upgrade need is not urgent,, Zen is coming next year. There is supposed to be more info available Dec. 12.
There are NO amc processor