Also, double check whether the mute stays on the screen or not. On mine it stays up for 5sec or so then goes away. I didn't realize this at first when I got my harmony and did just what jcb mentioned with several volume commands. If the mute stays on the screen and you do not have a discrete speaker off command, this will be your only option. You will have to send as many commands as it takes to get your volume down to zero from a typical viewing session - which could be anywhere from 10-50 (or more) commands depending on your TV and how loud the volume typically is.

I also prefer not to use the amp for all activities, only with movies or TV shows that include surround sound.