Adi;
I think Jeff must be some kind of amplifier salesman or something. According to his calculations, an auditorium sized venue would require more power than the entire east coast grid would supply. In the pro-audio business (which I have been an engineer for more than 2 decades), it is a common fact that a 3db increase in sound pressure requires twice the power. If you can get 100 db with 50 watts, it takes 100 watts to get 103 db. It's a basic law of logs. As far as speaker effiency not being an issue, that is an incredibly ridiculous statement. I've included a link that should clarify the relationship between speaker effiency and power requirements.
Danny

[Link: smr-home-theatre.org]