Coleman Audio M3Ph MKII - $600 (NE Portland)

This completely passive, uncolored controller lets you switch between three sets of speakers to ensure your mix translates to a wide range of playback systems.
L/R mute switches let you isolate stereo material and identify playback issues.
Can use with up to 4 different sources.
Used very sparingly in a home studio.
It is in excellent condition.
$600 OBO