I have the Zalman CNPS9500 on a X2 3800+ clocked to 2500MHz. Works brilliantly. Fully loaded, the CPU averages 37-42C, depending on the room temperature.
I think, however, that you're best bet would be to get a Sycthe Mine. This is supposed to be better than the Sythe Ninja, which is what every on here bangs on about
! Have a google for some stats and reviews. It's a pity that OcUK don't sell them though.
// EDIT // Yer, best read the FAQ before an admin gives you a fully-inclusive holiday, away from the forums.