I have a Sony receiver/amp connect to four outdoor wired speakers. My spouse would like to add speakers inside the house (kitchen, den, etc) so that the music can play simultaneously throughout I have a bluetooth receiver connected to the amp so we can stream from our phones). What is going to be my best option to add wireless speakers to this system so that it will play and be in sync with the wired speakers? Should I invest the $$$ in a Sonos Amp or Port, or is there a less expensive option?