Just to clarify, you want to be able to have two sets of stereo speakers (setA and setB) and you want to be able to switch between 4 settings to have a) No speakers (dubbing or just headphones, maybe?) b) Only setA c) Only setB d) Both setA and setB, and setB is going to be for outdoor use, is that right?
How big of an indoor space do you need to fill with sound, and how many people will be occupying it (max)?
How far away do you want to be able to hear the outdoor speakers, and are they going to be near someplace loud (airstrip, mechanic yard) or wet (port, rainy climate)?
Does it need to be 120v? 240v? Or does it have to be able to work on both?
Will the speakers need to be wireless/portable/repositionable, or are you ok with running cables?