Noctua NH-D15S Review @ OCC
 

"The performance is on par with the D15, which is really no surprise. The D15S is clearly built to keep the heat of overclocking under control with its massive dual towers and capable (and quiet) NF-A15 fan. Noctua's well-known SecuFirm2™ multi-socket mounting system makes the installation a breeze. If you have ever installed a Noctua cooler with the SecuFirm2™, you know what I mean. There are two key factors that determine the success of a cooler. One is a properly designed heat sink that can effectively transfer the heat away from your CPU and into the fin stack, and the other is a fan that can efficiently move air through the fin stack. The NF-AF15 140mm fan effortlessly handles this task."

http://www.overclockersclub.com/reviews/noctua_nhd15s/