unfortunately, its a nightmare to achieve a good cooling without noise at all!
I'm doing some "experiment" on my towerized A4K with some low rpm fans (PPC-Permedia and one blowing through the RAM).
Take a look to this modded 604e heatsink . . . almost finished
http://xoomer.virgilio.it/cieffeeditingvideo/CSPPC/the fan is a 45x45x10
