sometimes adding more fans raises temps. It is all about experimenting. Sometimes it works better when there is negative pressure and others its better with positive pressure.
There comes to a point also where you can add as many fans as you like and the temp still remain constant. Just make sure all the fans are blowing the right way.
but the more CFM the louder. And Dev, watercooling can only take you a certain distance. Remember that the water can NOT go lower than ambient temps. Thats the limit of water cooling. But its a different story when its snowing outside and you stick your radiator out the window.