As we have seen, heat is a problem for power amps. Even with switched supplies, heat must be regulated in order to ensure the efficiency of the amp, and to protect its circuits.
Power amps are usually fitted with fans that draw air into the casing to help keep things cool. However, with the air comes dust, so be sure that the fan covers are equipped with filters. Also, make sure that you clean the filters on a regular basis - Murphys Law dictates that if your amp is going to overheat, itll do it during an important performance.
The manufacturer Crown designed its K1 and K2 amps to operate without fans, using an ingenious convection system to release heat into the ambient air, and this method has also been adopted by some other manufacturers. While it helps to reduce the weight of the amp by doing away with the fans and their motors, and is perfect where low acoustic noise is essential, such as in small venue jazz and classical sound reinforcement, the technology is not cheap and is reliant on plenty of space around the amp to ensure a good supply of air. In some of the more compact clubs and pubs, that kind of space is not always readily available...