Another option that we chose:
We added the Internet option to our primary car Sirius/XM subscription for just a few dollars a month instead of paying for another "vehicle" subscription for the Precept as well as the installation of the module and the antenna etc.
We run our Sirius from an iphone plugged into the USB input on the Precept radio (we have a Clarion unit) utilizing our data plan when driving and wifi when in camp (if available). It also works on the coach's bluetooth as well as plugged into the outside radio's input
The cost of a slightly beefed up data plan and the Internet Sirius subscription is BY FAR less expensive than the alternative discussed here. Our dealer's PDI guy actually suggested this instead of another subscription.
The Internet subscription also gives us the ability use it at home and anywhere outside of a vehicle.
Just a thought for those considering how to add satellite radio to their new Precepts.