Saw Ten Years Later at the Long Beach Arena in the theater set up (a curtain cutting the place in half) and it was really loud. The opening band was Blackfoot and they were pretty loud, but it got louder. It was glorious, but loud. So yes, I would say the cranked Marshalls had everything to do with it.
1979Was that in 1991?
Loud amps from the era vibrate the strings sympathetically, that's where/how that incredible live Gibson into Marshall magic tone/sustain happens. Even better with a semi hollow.
I would think in heaven, you get three full stacks like Jimi did ;]