I am getting a case and it has a 120mm front intake fan built in (I don't know the RPM of it though). I am planning to install a AF120 in the rear for exhaust. I will also be mounting the PSU with the fan facing down so that it will intake cool air. So I have 2 intakes and 1 exhaust (as the PSU doesn't work to push air outside). Does that make my set up a positive or just neutral (making the intake and exhaust from the PSU redundant)? Would the difference in the RPM of the built in fan and the AF120 change things?