i say get a VANTEC AEROFLOW. i got one on my xp+2500 @ 2200mhz@ 1.7v
my temps idle around 36 and on full load its around 43 or something. it is super quiet as well, and pretty good for overclocking. its costs $49 at eyo.com.au
or if you want something with an adjustable fan, get the...