I just had an aftermarket Sirius radio installed in my '06 STS. I told the tech to power it on a circuit that will go on with 'Accessory' and turn off when the ignition is turned off but he could not find such a circuit. He plugged it in the fuse block that is located under the rear seat but could only find circuits that were just always 'ON' or would only work when the ignition was on. I want to change it to work when the 'Accessory' button is pushed but can't seem to find such a circuit. The best would be to find somewhere to power it that also has "Retained" power when the ignition is turned off just like the factory radio is. Any suggestions ?