If I have the Stealth XT bar connected to aux input, does the bar default to the aux input or bluetooth or what (I see it has no switched power input)? IOW at power up do I need to change the input from bluetooth to aux every single time? OR does it start on aux or somehow revert to last used? ALSO, do I have to power on the unit every single time (via a button) once power is restored or does it automatically turn on once voltage is present?