The cougar fans are a little bit noisier too, but that doenst mean it will bother you necessarally. the silenx fans are totally silent, you put that thing to your ear and you do not hear a thing!
BTW, this is the one you should go with:http://www.newegg.com/Product/Product.aspx?Item=N82E16835191013
and newegg has this model with green LEDs 1 dollar cheaper too....funny huh.. Im putting specs from the silenx and cougar below, if anyone is interested:
Silenex: 72CFM/14db $14
Cougar: 71CFM/18db $19 (this model can speed up to 120CFM, that that will hit more than 27db)
If the cougar is kept spinning at its lowest settings, its silent too (18db is great, you should avoid going over 20db). Silenx always run at a fixed speed, therfore fixed levels of noise