From the pictures you provided, can't figure out how you planned the airflow on that area. I can se that you have a fan in the back and some holes above the cpu. My question is, how you want to orient the Noctua heatsink? Will blow from front to back or from bottom to up? In either case you must keep the airflow direction on the fan inline with the heatsink, but you can inverse the other one (as an intake). I would place the Noctua to blow backward, the rear fan to exhaust and the top fan to intake. Maybe, also use a deflector for the top fan to blow toward the motherboard...