That's pretty bizarre sounding, ZoFo, but I do know of a couple cases when changing one setting will affect others. If you set the sub to none, the mains will "pop" to large. If you set the mains to "small" the other channels will follow suit. Also, there's a bug relating to the center and surrounds - you can't set both to "none" simultaneously (so with your center already disabled, "none" wouldn't be an option for the surrounds).