Another shout for the Bose S1 battery (or mains) powered PA here. I've had mine for several years now, and have used it for busking, and folk pub-jams.
I also used it for a couple of small, acoustic gigs. It's loud for its size, and very portable. It also has 2 standard jack / mic inputs, and a mini-jack for MP3 players / phones etc.
As has been mentioned - it ain't cheap, but much louder than the Micro Bass Cube. Quality build and sound though. Oh, and you can link them up if you have two (possibly more?).