I swapped my two NZXT AER exhaust fans in my H500i with a Noctua NF-A12x15 120mm PWM (back) and a Noctua 140mm NF-A14 PWM (top). CPU is a few degrees cooler, but
The Best 120mm/140mm Case Fan Shootout, feat. Arctic, BlackNoise, Noctua, and Scythe - YouTube
Amazon.com: Noctua 140mm Premium Quiet Quality Fan with AAO Frame Technology (NF-A14 PWM) : Electronics
Noctua Shows Off Fanless CPU Cooler, 140mm A-Series Fan and More | Tom's Hardware