Your PSU is just fine. Actually it's a great PSU and no it's not the source of your heat problem. You need better ventelation, and maybe a good aftermarket CPU cooler.
Get two 120mm case fans. Just be aware that even if you get "Silent" fans, if they push a high CFM, then you may get some noise from the air turbulence, especially if the airflow in the back encounters obstructions like being close to a wall. I'd say go with two of these