Routine maintenance is essential as amplifiers do suck in a lot of air through the fans which will leave deposits inside the amplifier and over time this built up can cause the amplifier to overheat due to the dust deposits inside the amp, compressed air is the best thing to use and will require the amplifier to be opened and the dust blown out PS make sure it's not plugged in when attempting this. If this does not improve the performance then it will need to be inspected by an engineer.