I have bought the Zalman cnps10X and I'm very glad with the results!
I'm running my core I5 on 4120 mhz with a core voltage of 1.57 V and the tempertures wont go above 63-65 °C (depends on ambient temperture) on 2houres full load with Intel burn
it takes THAT MUCH voltage to get 4.12Ghz out of yours?
Mine'll do 4.3Ghz on 1.44v - you sure there's nothing else limiting it?