Here is an interesting explanation of how amplifier power, speaker sensitivity and transient response all interact. This is part of a response Matt gave to an SRT installation concerning amplifier limiting:
"A normal listening level might be an average of 90db but transients peaks will go at least 20 db above that. In order to preserve those transients the amp will need to produce 100 times more power than is required to maintain the 90db average. Or, in terms of voltage, 10 times the voltage swing.
The SRT is around 90db efficiency at 1 meter from 2.83 volts RMS. That means 78db at a typical listening location 4 meters (~13 ft.) away. So, to produce 90db at the listening location the SRT needs 11.32 volts RMS from the amp. In order to preserve the transients it will need 10 times that or up to 113.2 volts RMS for very short periods of time. High perfromance amps like the Lab Gruppen are actually designed to do this and the speakers are designed to handle it."
I hope you found this of interest, Ken