Hi Glenn
I remember the days when I played a Hammond M3 (spinet version of B3) and at first used a Leslie, and later used a Fender Bass amp. Of course in those days an organist or keyboard player pretty much used a bass amp. Before the keyboard amps came out. As far as the PA, that was the other guys job, I didn't want to mess with all those knobs. haha.
I used a Rotoverb Leslie simulator which sounded great. Still have it as a matter of fact. Hmmmm, come to think of it I think I'll sell it.
Best
Scott Langholff