Andrew’s suggestions are also

Andrew’s suggestions are also good. The quickest sure fix is to add a fan to generate local airflow over the card. If you’re willing to experiment, you could also try installing both of the case fans such that they exhaust and then remove an expansion slot cover next to the InfiniTV. The idea here is that you are drawing cool air in from outside the case through the expansion area which then gets exhausted out by the fans after passing over the InfiniTV.

I’ve attached your picture with the potential fan locations. As Andrew said, cardboard, double-sided foam tape or velcro, etc. will come in handy for mounting the fan.