I've just grabbed an inexpensive (£9) Whisper Rock II (80mm cooler) rated at 26db and two YS-tech 80mm ball bearing fans (£4 each) pushing 27CFM@20db.
This is the quietest option I can find in the UK without dishing out loads of cash. Ideally I wanted the Raptorcool/FalconRock 1 with the three connector clip, 25db rating and a copper insert but no sign of these on our shores.
The WhisperRock heatsink 80mm fan (26db, 2800rpm) wasn't very noisy but had an annoying pitch to it so I replaced it with a YS-Tech 20db 27CFM fan - I love these fans!
Now my rig has a YS-Tech 80mms on the
PSU, exhaust and
CPU. I've left out a front intake because it seems to make little difference. No fan is individually louder than 20db making for a very quiet system.
In fact, all I can here now is the 7200rpm Harddrive - the fans are inaudible.
Temps? Well system never goes above 28 in a VERY warm room, 26 average in cooler weather. At the hottest ambient temps, the
CPU idles at 46 and hits 50.5 full load (socket temps).
Not bad. I'd say I'm running only 2-4C hotter than with a full kit of normally positioned noisy fans, but many, many times quieter.
For anyone wishing to have silence over performance, I fully suggest going for 80mm fans all round with db ratings no more than 24.