Is there no situation where the rear fan can be reversed into an intake fan for the purposes of achieving positive pressure along with the front fans, with the top fan becoming the exhaust?
There are some setups where a rear intake is ok, and others where you do sacrifice cooling efficiency... don't know if yours fit the former or not.
1)The rear fan should have a filter on it. For obvious reasons, I think...
2)Cpu needs to be custom or AIO cooled. If it's air cooled... no matter which direction you spin the cooler, it's a less efficient setup with a rear intake - not that the cooler itself is bad or anything.
3)Gpu needs to be custom or AIO cooled. This one's probably more important than both 1 and 2, because:
-If the air cooled gpu is a blower or radial fan model: these shove their waste heat right out the back. Once that heated air is outside the chassis, it will rise, only to get drawn right back in.
-If the popular and common axial fan model: these dump their waste heat inside the chassis. Instead of smooth transition up and outside, this heated air gets T-boned by the air coming in from the rear, and some efficiency is lost.
The air traffic should be smooth, or as smooth as possible, and a rear intake setup is most effective when both cpu and gpu coolers are liquid, because of the position of the radiators.