Marc, it may be helpful to me and others that wish to respond, that you provide some more detail of the amp or receiver you are trying to hook up to two sets of speakers.

If your amp is one that automatically decodes the 5.1 or 6.1 or 7.1 formats, then the speaker connectors take care of the front "large cabinets", and surrounds "the Bose pair", each pair connected to the correct speaker outputs. If you are talking of a stereo amplifier that has a selector switch for Set A, Set B, and Set A+B, does it have "surround" outputs?

If I understand you correctly, you want to be able to switch the Bose away from the surround connection to the "speaker B" connection. There is a way to install a switch wired in such a way to alternate between connecting the Bose pair to the surround output terminals and to the Speaker B output terminals. The switch is a 4PDT (stands for four pole double throw) type with 12 terminals, six of which is for the left channel, and six for the right channel. Do all work with the power on the amp off, or better yet power cord disconnected from the wall socket.

Usually the terminals are arranged in a 4 across and 3 down set, when the switch toggle is moving up or down. Typically, the center row of 4 terminals would connect to the Bose set, two terminals for the left speaker and two terminals for the right speaker. Then you can connect, say, the upper terminals (which are connected to Bose when the toggle handle is down) to connect to the surround terminals on the amp, and the lower 4 terminals (which are connected to Bose when the toggle handle is up) to connect to the Speaker B terminals. Make sure that the switch is "non-shorting" type, so that it CANNOT connect the Speaker B terminals before disconnecting the Surround terminals.

Also keep track of which column of terminals are which. In other words, if the left-most column is the "plus" of the left Bose speaker, connect the upper one to the Left Plus on the surround on the amp, the center to the left plus on the Bose, the lower one to the left plus on the Speaker B terminal on the amp. Then the second column would be the ground or minus terminals for the left speaker. The remaining two columns of terminals are for the ground and for the Right Plus respectively.

Mount the switch in a Project Box available at electronics stores and use strain relief for the cables. Alternatively, and slightly more complicated, you can use 12 speaker terminals on the box, two pairs each for the two outputs from the amp, and two pairs for the Bose, and internally connect the speaker terminals mounted on the box to the switch. This way, you can disconnect the box easily from the speakers and amp.

If you use this arrangement, make sure you flip the switch when the amplifier is turned OFF, in case your amp does not like speaker loads connecting and disconnecting suddenly. The switch and cables must be rated to handle more than the power (actually current) your amp can output.

If you're not sure or don't fully understand how to do this, please ask an expert before doing anything. I would not want you to cause damage to any of your equipment, and most importantly, not cause any harm to yourself.

Is there something wrong with your large main speakers that causes you to prefer your rear speakers? Using rear placed speakers for stereo listening can't be good for imaging.

If you have a 7.1 reciever, alot allow the back surrounds to be re-assinged as zone2 for remote placement, in your case if you were to go zone2 then your Bose speakers would output the source material you choose, years ago when younger and before my gear went up a few notches I used to use that feature for music in room while my fronts output game sound while I played Nintendo...wow I feel old.