One system, two amps...one for tv and the other for music

My preamp has dual outputs going to a decent low power (consumption) amp and the other to my Threshold S200 space heater. I only run the Threshold while doing serious music sessions and my small amp for tv and casual listening. My speakers have dual binding posts with a factory jumper. I'm currently swapping my speaker cables from one amp to the other. Is it ok to have both amps connected with separate cables but only having one amp powered up at a time? My concern is added impedance from the other powered down amp. I'm guessing this isn't a very good idea no matter how convenient it would be.