Yes enable it, it helps in better performance for the videos. And what is the total system specifications of your computer? Also tell me the make and model of your power supply? It shouldn't be going too hot. What is the temperature you are seeing on which you consider the graphic card to be hot?
OK that temperature is weird, it should not go above 70 to 80C. You sure that you connected the auxiliary power connectors to the graphic card? Are the fans working of the graphic card?