My 7075 has been running without fans since I bought it in 2009. It never gets too warm. But it also has a lot of free air around it. The heat sinks are sized so as to NOT require fans. Smaller heat sinks would be a bigger concern because they wouldn't transfer as much heat to the surrounding air.

That being said, if your amp is in a tight/enclosed space you might think about adding fans to move some air around.