Though I mostly got them due to cost reasons, i've been happy with my Arctic P14 PWM, $40 for a 5 pack and they can be daisy chained which makes things WAY easier for cable management.
Super quiet around 50% or below, they get a pretty good hum and woosh when pushing a lot of air at 100%. I keep mine below 70%, even at full load.
As suggested be quiet! Silent Wings 3 are quite good. I suggest the high speed ones, as other 140mm is only 1000rpm max speed to high speed model going up to 1600rpm. Sure, that is about 300-400rpm faster than usually needed, but sometimes it is needed. 120mm are up to1450rpm, with high speed being 2200rpm. I also prefer PWM fans.