Here is a link to the possible cpu upgrades.
http://www.ecs.com.tw/ECSWebSite/Product/Product_Support.aspx?DetailID=1356&CategoryID=1&DetailName=Feature&MenuID=24&LanID=0
Your A4-6300 is a dual core with a passmark rating of 2222 and a single thread rating of 1367.
It is the single thread performance that is most important for the gamer.
Few games can use more than 2-3 cores, but some games DO require 4 threads to run.
The A10-6700 mentioned above is a 4 core processor that sells for $140 or so.
It has a passmark rating of 4604 and a single thread rating of 1522.
That is a reasonable upgrade, but that will be as far as it goes.
AMD cores are weak and not good for gaming.
You buy a APU for the excellent integrated graphics.
But, there are no real good upgrades, particularly for a gamer.
If you install a superior discrete graphics card, you will have thrown away the big advantage of the APU.
Then, you are left with a relatively weak cpu. Most games depend on only a few fast cores.
The possible upgrades are to more cores, but few games will use more than 2-3 cores so more cores are not very helpful.
Bottom line.....
What you get with a APU is what you will live with forever.