I'm surprised that the discussion about replacement fans are more focused on their airflow volume (CFM) rather than static pressure (mm/H2O) which is more significant in heat sink/radiator applications.  High static pressure fans are more capable of penetrating through dense heat sink fins such as in the AntMiner devices.  I think there's a reason why Bitmain engineers equip their units with very powerful industrial 12038s with high static pressure (directly proportional to loudness) instead of just mainstream consumer-oriented 12025s.