Also, depending on the house layout one can sometimes discover a closet in the same joist space as a pair of ceiling speakers below.  If this is the case, the speaker wires can be rerouted through the closet floor to a Sonos CONNECT:AMP.

I've hidden Sonos speakers and CONNECT:AMP's in baskets. It looks like a display of ornamental baskets. Slide a SUB under a sofa and knock their socks off.