I have the HAF 932. You'll definitely have to remove the large fan at the top rear of the case if you want to install the power supply in the top. If you install a 120mm fan further to the front it kind of defeats the classic bottom front to top rear airflow.
Ventilation, airflow, and cooling with the stock fans are outstanding. No problem installing the power supply in the bottom rear of the case.
Saiello - I have the Corsair HX620 in the bottom of my HAF 932 with the psu fan on the bottom so it can intake fresh air and cool itself. The top side of the psu never gets very warm to the touch.