Hardware Extreme takes a look at the ThermoSonic ThermoEngine HSF for you...but they have tested it with both the mighty Delta fan and also the 40-CFM YS Tech model that has been going around lately. here's a snip:
"The heat sink is very impressive with the unique design compared to all those other heat sinks on the market. When reviewing and doing my research on the heat sink, I discovered the ThermoEngine has a solid center, with the fins being cut around the solid center. Also there's the intake cover, the fan is screwed down onto the heat sink, resting within the intake cover. The fan is set to blow downwards along the fins of the heat sinks and dissipating all the heat. This design is perfect for airflow from the fan."