selectable output mute feature

I'm looking for a preamplifier, which has multiple output and mute them selectably. Switching output A and B is also OK. Many preamplifier equipped with some parallel output, but they are always ON. I have two poweramplifier & speaker systems and would like to select them from one preamplifier. Any suggestion is welcome. Thanks.
McIntosh preamps are about the only ones with that capability. You can operate up to three independant systems with one McIntosh preamp. It is a great idea but so far, few think of it. I too plan on having two systems through one preamp soon. Good luck! Arthur
??? I thought a lot of preamps had a selectable output, it isn't something Mac has a monopoly on. My Theta has a "Main/Remote" switch.