In my case I used the Bryston 2 way selector box to at times run one pair of speakers, at others to run both at same time. As many amps/pre have no headphone output, I used it for headphone use as well. For more info if not found on the Bryston web site, one might check the audio advisor site. The Bryston works well, and seems built to last, with excellent sound quality. As with all such type, they present your amp with the proper load to protect the amp, and drive the speakers properly. Some units have a hi/low power switch, as is the case of the Russound speaker selector box with headphone output I also have. This older unit would seem dated as it uses a barrier strip for the speaker connections. I also believe Parasound makes a speaker selector box.