Well the case has 4 fan slots and I would use all of them because I like good airflow. Of no radiator is taking up fan spots go ahead and put two 140mm AF fans in front(if there are no drive bays otherwise SP fans), one in the back and one in the top. The back and top ones are already included but if you want to replace them the rear accepts 120mm, so an af120 fan should do, and the top go ahead and put an af140 fan.