I use a 400 cfm fan for intake and a 165 cfm fan for outtake. They are green made by hydrofarm you can find deals on the internet for them. I bought a router controller for each of them and can control their speeds with it. I have mine going through a 9000 can and its perfect like that.anyone? ;O
The quietest fans i have ever heard are "RUCK FANS" and if you want to silence them more use acoustic ducting with it. I have one and its hard to hear.anyone? ;O