Depends what you want most. Performance, or silence, or both with a fan controller?
Merlin's suggestion with the Noctua P12 fans are absolutely silent and do not require a controller whatsoever. To stay silent they don't push huge amounts of air though.
Thumper's suggestion of the Silverstone FM121 are very dependable fans that push an incredible amount of airflow at speed. They are only silent at the absolute lowest fan controller speed (to my ears), anything higher and they get loud fast. I can't run one of them without a fan controller, they're just to loud for me.
Core i7 4770k 4.2Ghz
Crucial Ballistix Sport LP 1600MHz 32GB
EVGA GTX 480 HydroCopper FTW
ASUS Xonar DX
Corsair Neutron GTX 240GB | Windows 7 64-bit
Apogee XT + MCP655 & Thermochill Triple 140mm Radiator
Corsair AX1200 PSU | Cooler Master HAF-X