I have a 2006 Silverado 2500HD with XM radio. Is there a jack on the back of the radio or somewhere else where I can easily connext a Sirius receiver? I know on the 2007s there is a jack on the front of the radio where you can plug a Sirius radio (or iPod) and access it by pushing the aux cd button. I have the aux cd button on the front of my radio, so I assume there is a place to connect another device.