in dash cd player negative to switch all speakers off

ive got a convertible and i would like to have a tailgate party box to throw in the back seat. i was wondering if i would hurt anything by putting a switch between all four negatives on all four channels before it goes out to the car door speakers so i can switch them off so i dont have to hear any of there low quality noise. all four share the same negative on my home theater amps, aswell as what i can tell when i take the deck apart. does this spell disaster? good thing walmart has a great return policy lol.