At that point, you'll want some sort of tone generator (the niles piece is in place at my house, so second that recommendation), some sort of line level audio unity distribution amp (xantech av61 for example), some sort of line level audio switching device (if voltage activated, pay attention to ma requirements) (if I am reading it, the crestron amp is fed by an external matrixing preamp), and you'll be good, as long as the crestron stays ready to play.