You can reach 5GHz if you want.. Its called Electro Hydro Phase change cooling... and it works like a dream. However, if you want AIR cooling that is VASTLY superior to other coolers, then I will provide links to both.
ELECTRO HYDRO PHASE CHANGE COOLING:
Then go to
MCW5002-775T™ LIQUID COOLED THERMOELECTRIC ASSEMBLY FOR INTEL® PENTIUM® 4 (LGA775) PROCESSORS under the Thermoelectric Assemblies.
This Zalman cooler is PURE COPPER, and uses a GIANT 120mm fan to directly cool the processor. Expect temps of around 35-55C full load.
Overclock till you puke!