It would depend on case configuration, fan placement etc. Usually well placed fans with good airflow paired with a fan controller is the best way to help maintain ventilation and keep noise low. I used to think noctua's were expensive too but they're really not much more expensive than corsair's, phanteks or other decent quality fans. Noctua also make a redux version of their fans which are around $19-20 for 140mm pwm models with a two tone gray scheme that gets away from the original colors. Since moving to a case which supports 140mm fans and getting away from 90mm/120mm fans I've been pretty pleased. Not a single 120mm fan left in my case. The smallest (and loudest) fan is still my gpu fan.