When are they gibing?
What kind of wall speakers are you using? In wall or surface mounted?
For the wiring with the brush plates i'd pass the wires through the flush box and tape them all together. No point leaving them tucked inside the wall if they are going to end up out later. Tape them up so that they don't get painted and so that as a bunch, they protect each other. Gib fixers / painters might have a moan, but who cares.