3 fans - 1 on top of the case; 1 on the back; 1 on the panel that comes off.
I'm just looking for some advice concerning my rig. I've been told that my case is a little bit small and I just got my PC back from repairs and everything is running well. Will air cooling be sufficient? Should I even risk to OC my rig and will it even be worth it?
Your case is good enough for overclocking using an aftermarket air cooler. It is also wide enough since, as a rule, anything over 8" wide will usually accomodate the largest of air coolers.
As to whether it will be worth it... the performance increase is undeniable but, there are risks (they're really minimal IMO) which you'll need to consider. I would read up on overclocking the 870 processor, your graphics card too (if you haven't done that already) and, research aftermarket coolers. FrostyTech and Tom's are both good sources for that.
My take is that it is worth it but you should tackle it only when you understand what you are doing, how to go back and the kind of issues others have had.
Oh yeah, many computer games are still heavily CPU bound since most of the graphics and physics engines were created before the advent of multiple cores and super graphics cards. The thought then was that CPU's would just get faster and faster. Developers have only recently started binding those engines to the GPU's and multi-cores. Some games such as Microsoft's Flight Simulator X barely use any graphics resources still and can't even use more than two cores - but it sure loves overclocks. You can look up which helps more by game (each title is different in how dependant it is on specific hardware)