Mordenmail...Audio amps are designed today with power supplies capable of continuously delivering a certain level of output voltage. Some time ago some amps were designed with power supplies that could deliver high voltage, but only for a brief time interval. For this brief time a high power output could be measured, for example 100 watts for 1/2 second, but only a much lower power could be delivered continuously. Although there is some logic to such a design because music power only peaks briefly, it was criticised as false advertizing, and now all amps are rated for continuous power and designed accordingly.
Bottom line is that if you want high voltage swing you will need an amp with a power rating well in excess of the actual power of the music signal.