i have emailed sirius for a complete list of units which are capable of "sirius everything plus the best of xm" but they only sent back a list of plug and plays which are capable, and asked for the esn# for any other unit to determine if it's capable of sir/best xm. i don't have any esn's--i'm just trolling ebay,craigslist, etc. for a "component" style sirius receiver which can pick up the "siri every/best xm" package. anybody know about the 550, or a place to find out which units are capable of this package ? thanks