"Why NOT use fans???" "Of course I am a construction worker and noise is a part of life"
Think you answered your own question.
I depends what you want, and how quiet the enviroment you are in. I got down to jsut 1 80mm in the PSU at 5v and that was annoying to me. It's not just about db rating its the type on noise and fans to me sound horrible because they are messing with sound transfer medium.
If they don't bother you great, but try to understnd why some don't want any. I have none and it's the way it will stay, If other parts of the sytems requre extra cooling because of it I'll get around it without resorting to fans.
The only "silent" fan I've come across myself is the one that is disconnected.