My h50 also has a push/pull setup going on. To compensate for using the rear 120mm exhaust fan as an intake I've mounted another 120mm fan in the front of the case right below the dvd rom to maximize air flow. There is also an 80mm fan in bottom front that works as an intake to feed the video cards with cool air.
There is your issue, you using front and back intakes, the air is gather in middle of case and not escaping, you need to create a tunnel through your case, the fans on the H50 needs to be turned around.
