Over the years I've played places with and without PA systems of their own or ones that were pretty crappy. My groups worked with full PA and monitor systems but that is a real hassle to hall around and set up. I own a Roland SA 300 Stage Amplifier that I can transport easily since it's light and not too big. It seems to be an out growth of the Roland AC 60 and 90 acoustic guitar amps. In a pinch I have even used my AC 60 on its own; one channel for guitar and one for vocal mic. The SA 300 Mixer/Amp/speaker cab unit is about the size of the AC 90 but has four channels and lots of ins and outs. It can mount on a pole and houses two speakers just like the AC 60 or 90. The other part of the system is a bass cab that the top unit can sit on, like a small electric guitar combo amp. I've used it live at coffee shop gigs with my friend Bill who plays bass as well as guitar and we both sing and I play guitar. It was plenty for a medium sized coffee house gig. Their own system sucked so we just didn't use it. Because there were two of us, I took along a small TC-Helicon VoiceSolo VSM-300 Active Voice Monitor to let us hear the mix. Along with my guitar, it all fit in my car with no trouble, was easy to carry and set up and sounded great. I can use just the mixer/amp/speaker cab top part of the system by itself just like an AC 60 or as a mixer / monitor and patch the output into an existing PA System and play larger or more complexly shaped venues using the existing power amp and speaker arrays.
I love this thing and best of all, while it sounds great, it is also less expensive than the Bose system or even using a Mackie powered monitor and a small mixer. Sure, I'd love to use the Bose system but the speaker array and the bass module are pretty expensive, same with the Fishman Solo amp. The Roland SA 300 works great for me and is worth checking out.