I have a PJB briefcase and it is surprising loud, but not quite enough to keep up with a not-very-loud drummer, keys, guitar and vocals at a rehearsal. It's also damn heavy, with a battery in it weighs more than my Tecamp Puma 110 and isn't anywhere near as loud.
But it does sound lovely with double bass, or anything else at sensible volumes - bass guitar, acoustic, accordion, mandolin, bouzouki, even banjo.