Ok here is the breakdown you almost never want that rear fans set as intake heat rises so since on most case that fan slot is up much higher it will take all the hot air with it if you are worried about that fan pulling air through your heatsink it really wont and what air it does pull through it wont effect performance that much seeing as you have a VERY high tdp heatsink which will be plenty to cool your CPU so i would recommend putting the fans at the front of your case as intake and that rear fan as exhaust and put those fans on top as intake. Hope this helped!