I have a 2004 Chevy Tahoe with XM, factory DVD, and on star and would love to add my IPOD. I would really like to keep the XM and factory DVD. I know I can hook up the IPOD though the DVD player or an FM modulator but I want the best sound possible and I want to control the IPOD though the radio. Is there an inter face I can buy to be able to keep the XM and DVD.