The XM lineup is a set lineup. They sometimes will add a station but it does not happen too often. Here is the current channel lineup:
http://www.xmradio.com/programming/f...sp?sort=number
The price is 12.95 a month for a subscription.
As far as a portable unit you can use in both your home and car I would recommend a Myfi which is a portable unit that comes with a home kit, car kit and you can also use it as just a portable unit with headphones.
Other cheap units include the Roady2, Skyfi2. With those depending on how they are sold you have to buy seperate home kits or car kits.
As far as hooking into your stereo I am not sure exactly what kind you have but these radios can play over an FM frequency in your car or if you have an AUX input they can be hooked up through that or through a cassette adapter.
A very good site for XM info is XM411.com. That site also includes a store which is probably the best place I have found to buy XM equipment. They have good prices and always ship items out quickly. You can also buy XM equipment at Best Buy, Circuit City, Sears, Walmart and others.
If you have any other questions let me know.