Need to know about satellite radio

Is Sirius XM the only service available now? Do the receivers require a special antenna? Can one unit go from house to car? Is there a flat rate to pay for all the channels? About how much is the monthly charge? Is there a difference in receivers (to justify higher price in some)?

I want to hear more classical music than is available on local stations, and am considering satellite radio. But I don't know much about it and would like someone to give me an overview.

If there is a good place on the web to read about basic setup I would like to know about it.

Thanks!