where he said they (him and Malcolm) each had SIX 100 watt marshall
Yeah Mr P that's right but what they have ONE main amp (a 50watt Marshall JMP with preamp, crank the shit out of it to pull the sound by driving the valves), and then feed into whatever many 100watt heads they need for sonicness/bigness, then feed the speaker boxes for wall of sound, then P.A it to make go far and wide (so you can hear it from your house).
Yepp you're dead right there. Just remembered an interview on "The Guitar Show" on the ABC where Angus said pretty much what you just described (one 50watt head to get the 'out front' sound, and the 100 watt heads for his on stage sound/volume).
There is no way any band use a row of Marshall quad boxes plugged in at real volume for the simple fact that the band would go deaf real quick and it's as simple as that, that type of gear is damaging and honestly any human would be physically 'moved' if you stood if front of it. Don't believe me?? Come around to my brothers place and see if you can keep your feet 
. Mainly boxes are set up for show, the P.A does the work (as well as the tubes).
hell yeah.. I TOTALLY BELIEVE
I KNOW how loud just ONE Marshall stack can be going at full guts!! I repaired a couple of old 70s Marshall heads for a recording studio in Tamworth, so i can vouch for just how loud they are(should've bought them when i had the chance). You're right NO ONE could stand in front of a row of Marshalls at full volume. They''re all there for show. How about Ted Nugent who in his earlier days supposedly used SIX fender supertwin amps all hooked up.. now THAT would be impossible, my father owns one of these amps and they are F**KING LOUD!! (all valve, 180 watts!!) these things would have to be one of the loudest guitar amps ever made!
