Hi Eric,
You can achieve this by creating one or more aux mixdown channels. See the tutorials page for a basic aux mixdown set up:
www.hauptwerk.com/tutorials
With this you can route everything to both sets of speakers (or even another pair using a second aux mixdown) then compare side by side by turning speakers on and off or by reducing the aux send level adjustments to -99dB for the pair you don't want to hear.