well if you want practically silent... and dont plan on moving your computer a ton... this thing is insanely awesome
http://www.newegg.com/app/ViewProduc...118-109&depa=0
my friend has one... on the higher speed setting you cant even here it over his low speed 120mm fan
and it keeps his cpu really cool
problem is its reallly heavy so you gotta be careful moving the computer around... and its huge... so it might not fit in all cases/motherboards...