Case Fans - What to look for?

[Egon]

I'm looking for a quiet case fan to act as an exhaust at the back of the case. First of all, this is a 2nd PC, not going to be used for anything extreme so my main concern is quiet - prefereably almost silent !

Can anyone reccomend me something quiet, I have to admit case fans aren't exactly something i've ever bought !

 

[Egon]

Yeah but I don't want to spend money on a 2nd PC that is only do a little bit of serving. My main rig doesn't even have watercooling.