I have XM in my pickup. When I want to listen in the house I just pop it out of its dock and plug it into another dock that feeds my Bose Wave radio with the output. Simple and one subscription.
So if you have the receiver model that is built-in to your car, you need another subscription if you want to listen in your house.
I was relating my research. I wanted a clean installation, not some Rube Goldberg contraption.