Zalman CPNS 7000 Al-Cu, 92mm fan and a speed controller
runs at 20-25 db depending on the fan speed.
I've just built a pair of 3.2 Ghz P4s using them on an ASUS p4C800E Deluxe mobo, Papst silent fans throughout, acoustipack foam lining and a Zalman silent PSU.
The Zalman mounting is dead easy btw.
As for the performance, I've been geting CPU core temps of about 29C when idle on one, and a little higher on the other (must've used a different amount of Artic Silver 5). The noise level is extremely low. The noisiest components are now the DVD drive, followed by the HDD. Although you're not supposed to run in silent mode on a P4 3.2 according to Zalman, I've quite happily throttled back the fan to 1600rpm, and only added a couple of degrees to the core temp.