At the risk of repeating myself or seeming a jerk, IMHO the peak volume level that can be generated is largely beside the point.... Where distortion isn't perceived as a negative, ear-splitting levels can be achieved with relatively "low" wattage, as proved by my 40w Fender Super Reverb 4 x 10" tube guitar amp.)That is true if the music has little dynamic range (meaning the difference in volume between the loudest notes and the softest notes). Most rock recordings fall into that category.
However, for music with wide dynamic range, such as well recorded, minimally compressed classical symphony orchestra, peak volume capability is most definitely not beside the point. On that kind of recording, power requirements for brief peaks can often be literally 1000 times or more as many watts as for the average volume level within the same work, which would correspond to a peak-to-average ratio of 30db.
Best regards,
-- Al