SLK 900 needs a fan, but you don't need to slap a tornado on there to get good results.
The slk-800 I have in my system keeps my cpu @+/-35c at load, conversely the MC462 I used to use had the temps at 44c under load. PLUS the MC462 was a PITA to take off and put back on.
GO with an 800/900 slk and you will be happy.
ps. remember: too much ASIII on your DIE will cause your temps to go higher. A little goes a long way!