Another vote for the Alpha's. I have both the PAL35t(best for S370 mainboards) and the PEP66, which is recommended for Slockets. I leapt before I looked when I bought the PAL35t. Mistake, because I finally decided on a Slot 1 mainboard. Live and learn. The PAL35t can be hung on a Slocket, but you loose the first and second Dimm slots. And it puts strain on the Slocket, because of the leverage of its weight.
I installed my PEP66 yesterday. It does a spectacular job, especially with the Delta 38 cfm 60mm fan. MY QII Crusher Timedemo CPU temp fell to 47C. It was 67C with a small hs. My idle temp fell to 33C. It was 44C with the little Si5 hs, with the "Black Label" on it, btw. A wind tunnel fan does nothing without a big hs.
The PEP66 fits on an Iwill Slocket II just fine. It's a little bit of a challenge to assemble, but the instruction sheet is better than the one that came with the PAL35t. I ordered mine from .millisec.com on Tue the 18th. It arrived on Friday the 21st. FedEx 2-Day would probably have delivered it three hours earlier. But millisec shipped it Priority Mail, for four bucks. Would three hours earlier be worth ten bucks extra? Not to me!