The real test for a high efficiency speaker is if it can be powered by an 1W amplifier and reproduce the entire frequency range (including bass) with 1W or less. Here is one review that covers such a system: http://theaudiobeatnik.com/linear-tube-audio-mz2-s-originally-released-microzotl2-0-teresonic-magus
high-efficiency loudspeakers
What is the best high-efficiancy loudspeakers? If you have it, are you happy ?