I picked up a Corsair H50 liquid cooling unit for my alternate rig a few months back. It keeps very stable temps for a Q6600 @ 3.6GHz below 60*C. Cant remember how much exactly though.
And the unit is completely self contained, no maintenance reqd.
I haven't tried changing the fan yet (alt box and all), but I imagine a decent yate loon or similar fan would do better still.