A couple of things to know up front about satellite radio.  First, for XM or Sirius, you need a receiver that is capable of receiving satellite radio.  Every major car and home audio company puts satellite radio into many of their tuners now, so you'll have lots of choices (Alpine, Clarion,  Pioneer, Sony etc).  The costs vary a lot, from a low of about $30 (after rebates) for a small one to a boombox style at around $150 to $1000 or more for an great tuner/receiver.  The total cost of the package in my car was about $700, which gave me a nice professional installation of a great sounding car stereo with speakers that plays not only XM stations, but also AM/FM and cds.  My friend opted for a portable, Walkman style XM radio for about $200 that he carries around everywhere.  You can also buy small portables that plug into the back of receivers/radios that have AUX inputs, and will play XM through the system.  Prices for XM and Sirius receivers are about the same. A lot of new cars come with XM or Sirius as an option, and a few offer a choice...look for it when you buy a new car.  XM has a better selection of hardware and systems.