Bernie,
My voice goes into the internal speakers through the dedicated mic input. The (s-950)aux in takes a signal from my Bose mixer that has the iPad, guitar and guest mics.
I never set feedback, and I have a great representation of the total mix BEFORE it goes to the house ... if at all. Tonight, I'm at an upscale country club at the Jersey Shore. Upscale means they hardly talk to me, all dress alike and tip better than average. (weird, huh?) I'll use the Bose angled away from me to point into a second room, and I rely on the Yamaha internals to cover the room I'm in. It's a background situation and the first 2 hours are quiet and reserved. I sing almost every number, but it's easy, middle of the road stuff that kinda "sits" under their conversations, rather than crashes on top of them.

The Bose Compact will hardly be turned up at all .. it just adds some fullness and bottom to an already "READY" mix.
Good luck!