Arma and dayz do not use more than a couple of threads so you would need to get an i5 to see preformance improvements in those games. I don't know about CS though
If you are only gaming with minimal apps running in the background then any difference will come mostly from clock-speed when comparing those two chips. At default speeds the 8370 will definitely give a higher FPS, if you OC the 6300 to a comparable speed then the difference will largely melt away.
The ARMA engine will generally try and use 4 logical processors; but you will always observe one of them being more heavily used than the other three. This is the main process and the only way to get it to run faster is to have a stronger processor core or reduce the amount of work it is trying to do.
I found that the ARMA games can usually be made to run quite well on AMD FX processors but you have to compromise a bit more than Intel CPU's due to their weaker core performance/IPC. Try dropping the Visibility and Object View Distance down.