Case Fan Setup

[JBails]

The case I am buying comes with one fan, and I'm buying three extra so all of the available spaces are used.
My problem is, my case doesn't have a fan mount on the top, just a grill. So I was wondering where my second exhaust should be.
The mounts are on the front, side, bottom and rear. From what I was taught, the cool air should come from the front, bottom and side, so will one exhaust fan at the rear be enough?

 

[kiezz]

what size are each fan? one exhaust will be enough you will be supplying plenty of cool air and most high end gpu's the fans are exhaust as well as the psu so its not any harm having positve pressure in your case the only downside i would say is you will have to keep the rpm of the exhaust fan at a moderately high setting, what case are you getting?

 

[JBails]

All fans are 120mm Fractal Design Silent Series R2. The case is a Coolermaster K380.

 

[kiezz]

looks good, I don't see any problem with that set up, if your using a standard aftermarket cooler mount it with the fan blowing air to the exhaust fan and you should have a good set up