I don't recall Glenn Miller even NEEDING a PA other than to reinforce the singers and the bass and piano a bit... Why do we all of a sudden need thousands of watts for music that never needed it in it's heyday? Are we all so much deafer now?! Are the dancehalls THAT much bigger? Glenn Miller probably played Carnegie Hall (if not, many others like Paul Whitehead DID). How many watts do you think HE used?

Please also don't forget that, even if the PA is in mono, the audience WILL hear positional cues from the spread of the musicians themselves. I am pretty sure that, no matter HOW many watts their PA is, for a big band gig it won't be turned up to the point where you CAN'T hear the musicians themselves..!

This is where large ensembles, and arrangers that try to SOUND like large ensembles differ. Subtle positioning cues help reinforce the illusion that there IS an ensemble up there, when in reality, it is just us, and our arrangers. A real ensemble even with a mono PA will still sound stereo, but a mono arranger will sound COMPLETELY mono, something that NO live band ever will.

Once again, JMO, yada yada yada.