If a speaker selector is what you are looking for, I would suggest one of these. I use mine to switch between two sets of tower speakers in my family room. Works great.
It sounds to me that you are looking for an amplifier switcher, one that is used in audio stores to A-B amps and speakers. I have no experience with this product but it seems to do what you need.
If neither are what you are looking for, Macdadtexas' suggestion will definitely be another option.