the best fan ive ever used, or have seen used are these:
http://www.newegg.com/Product/Product.aspx?Item=N82E16835214001
http://www.newegg.com/Product/Product.aspx?Item=N82E16835106133
and ive heard good things of yate loon and silenx.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835214001
http://www.newegg.com/Product/Product.aspx?Item=N82E16835106133
and ive heard good things of yate loon and silenx.