My original 2005 Sportster R finally died. It is always acquiring signal. I tried the antenna with a friends newer unit and it works fine. Sirius have tried the master reset and all that. I have the home dock and a boom box that I would like to still continue to use with the new replacement unit. What options do I have that are backwards compatible? The new unit life and signal strength are also a concern. The FM modulator is how it will be hooked up most of the time and this will be 1 of 3 replacements on the lifetime subscription plan.