It's really up to you. Given the audience size, some Artists don’t need a PA system for their Threshows.
If you'd prefer to use a PA system, be sure you check with the Host beforehand to make sure loud noise isn't a problem at their venue.
If you're looking for a great sounding, portable PA, check out Bose's L1 Compact System.
It's not cheap, but it's super easy to carry and sounds amazing. And, no, we don't get a kick back for saying that. 😀