Providing your system set up can handle it you can never have too many fans , just make sure they are set up right , intake on front and side , exhaust on top and rear and the cpu cooler pointing to the rear exhaust fan.
Some intake fans can make a cold draught on your hand due to the shape of the blades and fool you into thinking you put them the wrong way round so try this .... if you cant see the airflow direction arrow on the fan housing get a small piece of paper and place it up to the fan on the outside of your case , let go of it and if it does not drop on the floor its sucking air in.
For exhaust fans , after your pc has been working hard for a bit you should be able to feel warm or hot air blowing out onto your hand
Two front intakes and a single rear exhaust is typical and effective.
Top exhausts tend to divert cooler air out the top before they can get to the cooler, motherboard and graphics card.
Rear exhaust is better.
If anything, increase the rpm of the front intakes to get more cooling air into the system.
Haven't a few sites shown, that when there aren't many fans being used and there's an odd number(such as 1 or 3), that more exhaust over intake wins? Once you're past the magic 4 number, it doesn't matter as much, and you start going into diminishing returns territory.
Well, more exhaust over intake almost always wins for just cooling, but that's not the point.
I would be interested in links regarding the intake vs exhaust equation.
It seems to me that ultimately intake airflow must equal exhaust or pressure would build.
Whatever comes in must exit somewhere taking heat with it.