I guess if you do want the best cooling fan get a 120mm. They can be semi-quiet and and blow a good amount of air. Trust me, you will want a quiet fan.
Thats were the Speed adjustment is a plus .Actually i had a case with 2 80 mm fans in the rear and a 80mm in front .The 2- 120 mm Enermax fans are quiter but move 4 times the air volume .Crank it up or down to meet your needs .Of course your case has to accomidate them. I bought the Antec P120 case because of the 120 mm fan bays.