"There are a couple of valuable observations to make from the results. The most important is the dramatic cooling performance the IXG-80HA2 has when combined with the fan kit. If you compare the stock cooler at 100% with the IXG-80HA2 with fans installed, you will find approximately 20% cooler temps in an idle state and around 30% better under load. Impressive! Almost as dramatic is the cooler's ability to remain effective without fans and operating in silence. Yes, the IXG-HA2 with no fans performed on par with the stock cooler at 25%. As a word of warning, the copper heatpipes on the heatsink get very hot when used passively."
FULL STORY @ OVERCLOCKERSCLUB (http://www.overclockersclub.com/reviews/silenx_ixg80ha2/)