^ No disrespect for such a nice bro but I also know that cooling is not proportional to fans..
My concept:
ok, lets start with why I choose all 120mm, actually, the front 120mm draws air in and the
Rear 120mm throws it out (this is the basic thing). Now, we add a Side 120mm intake to cool the CPU and the GPU and it helps the two to maintain airflow by maintaining a chain. Now, the top fan, when air is trapped as it is extremely hot,
rises up, this air is thrown out by the TOP 120mm exhaust. Now one socket is left for the pressure exchange and to maintain pressure, this allows the air to go in and out as per requirement.
This is totally cool system with the near best pressure availible as no hot air stays inside and coll air is drawn in the same proportion, its actually a chain of airflow.
Thats what I think..
@OP - Bro, This is for maintaining the same pressure as the environment, Its the best as no air atays inside and every fas plays its part equally.