I am currently cooling my SB with an Enzotech Forged Copper heat sink (CNB-S1L), and a 40mm Silenx Ixtrema Pro Series fan. (Rated at 14dBA, and 5CFM)
That little bugger cost $17.00 at Micro Center... ;)
http://img149.imageshack.us/img149/4844/pic069ok4.jpg
Is the Silenx Ixtrema Pro a good fan, as 40mm fans go?
Is there one that might do a much better job of cooling my SB?