You should using the incoming and outgoing fan within 10 percent of space from each other. You should have insert air fan on the front, side and at the down of the cabinet and exhaust fan on the top and back side of the cabinet. If your exhaust fan is larger than the cooling fan then more air will pass inner of the system then the quantity of the air that is going out of the system. You can too utilize the fan control to keep the fan velocity and its rpm. Ever go with the form that will keep the lowest temperature in your system.