Unless you live in a hot climate and/or overclock it like mad on 2 volts, the slk900A is the best choice. Its a revised version of the 900u and fits 99% of amd boards and is lighter, smaller and clips on rather than having to take out the motherboard. And its only .5-1C hotter than the bigger U version. With a smartfan 2 on medium setting, expect excellent cooling while keeping things quiet. Or if you want maximum performance while still keeping things not so audible, use 2 smartfans on low-medium setting. I have this combination on my SK7 and overclocked 2500 @ 2.3ghz/1.8v. They are both running at a very quiet 3,200rpm and keeping my cpu under 50C most of the time. Right now im idling at 43C (20c ambient), even at 1.8 volts.
<A HREF="http://service.futuremark.com/compare?2k1=6868334" target="_new"> MY RIG </A>
<A HREF="http://service.futuremark.com/compare?2k3=1150155" target="_new"> 3D-03 </A>
<font color=red> 120% overclocker </font color=red> (cheapskate)