Time for an add in GPU, an APU upgrade won't get you far a couple of FPS more but an add in card can really increase performance.
My daughters APU machine play games quite well when I popped in my r290 from my broken machine, of course an r290 is overkill as the CPU probably can't back it up but those or something similar is available secondhand and you'll get more than 5x the performance for the outlay of a new CPU which would get you no where near the performance of a decent discrete GPU, its unlikely a Zen APU would do it either and will come with much higher expense in board, memory and CPU.
My example 3d Mark
a10 5700 with iGPU
http://www.3dmark.com/fs/11038535 (7660D is how iGPU shows up in windows)
same CPU with r290
http://www.3dmark.com/fs/11044384
Compare link
http://www.3dmark.com/compare/fs/11044384/fs/11038535/fs/11108910 including both of those and equally poor Intel CPU I used to test my board, though I did OC the 290 when in the Intel board, so not too fair, blimey my 8yr has more power than me at the moment
I could probably tune it more to be faster but I wasn't that interested, I was just after something functional and ran them out of interest

You notice the A10 CPU seems weaker on the iGPU that with Discrete GPU, this is because I OC'd the GPU and the CPU and the stock heatsink could not contain it whereas discrete GPU disabled on iGPU and the stock cooler could contain it.
An A10-7850K is going to get you around 1400-1500 3dmarks in that same benchmark and your a8 will be a little slower unless you have tweaked the
**** out of it due to clock speeds and less shaders.