Amplifiers

Power amplifiers are classified according to their design. In audio the classes A, B, AB, C and D are used.

The subject is very well covered here.

Class D is very efficient, more then 90% of the power is used for the music signal. In case of Class A 50% of the power is dissipated as heat..

A modern Class D amplifier can deliver 320 Watt at 4 ohm in an almost Mac Mini size package. If global warming (or a low electricity bill) and a good sound are your concern, these are the ones to go for.