[jackweasel]

I forgot to mention, in my earlier response, that you might want to visit the Bose Musicians forum and check out some of their "sketcher" posting. It's a way to position the Bose unit[s] and signal routing, to get the most out of your set-up. They have them for bands of all sizes and different instrument combinations.
My personal thought would be add the second Bose, put one behind each of you stringed musicians, with the drummer set up in the middle, slightly behind. With an L-1 on each side and slightly behind him, he could hear the mix much better and everyone's working off the same "monitor" and that's what the audience is hearing.
They've got a great community of users and you might even be able to arrange for a loan/rental of one for a real live test-drive. The T-1 module also has some vocal effects and you can store your own personal settings. If I could afford it, I'd get one to add to my model 1. That would give me seven inputs on one l-1.
Check it out.