FWIW, there are a number of quite impressive coolers around (at a price).
The heat-pipe types are particularly effective, and yes, the Zalman's 
are good.
These people have a wide range, including both heat-pipe and water coolers.
http://www.overclockers.co.uk/productlist.php?groupid=701&catid=57
Sadly few manufacturers or suppliers quote the performance of their 
coolers in an absolute form one can use for calculation.
Incidently I've seen people buy big, expensive, coolers that keep their 
CPU to "below 40C, so well worth the cost". If you're not doing risky 
things like overclocking, your CPU should be fine if you keep it below, 
say, 80C. You'll not destroy it even if it gets to 100+, but it would be 
at a higher risk of misbehaviour.
I second the view that the other fans will likely notice once the CPU 
fan is quietened.
Gordon.
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