Just to let people know than one of the best curent solution to cool your cpu (when it comes to efficiency+silence) is the Noctua NH-U12F... It is quite big but afford a 120 mm fan that allows slow speed for a very good efficiency. Furthermore, i have an intel board (D975XBX2) and, while the chipset aluminium cooling system is high, the new versions of the Noctua have been modified to cope with such a problem : the lowest fins begin at a higher lever to avoid problems with other components. As for the silence, man you cannot ear it....
Just my experience ; hope it helps.
Jo