I own a Lian Li pc-7 and it comes with 2x 120mm fan sockets and 1x 80mm fan socket.
Currently i'm using 1x 120mm intake at the front and 1x 120mm exhaust at the rear. Both have same cfm but intake slightly less due to fan filter. I'm also using a PSU that uses 1x 120mm as an exhaust. So i have 2 exhauts and 1 intake. Is it adviseable for me to use an 80mm fan as an exhaust on the top of the casing?