Vantec's AeroFlow - $25.00
http://www.newegg.com/app/ViewProduc...110-007&depa=1
I my self find it very quiet, but then again anyone who has more then 3 normal 80mm fans wont even hear it anyways.
For the excellent job it does cooling vs other coolers in its class, its dead quiet.
And dont let TMD fans fool you, they once were bad news, Vantec has perfected it.