2. SkyFi2 , or if you can afford it, the MyFi by Delphi
3. The SkyFi is a detachable unit. You can attach it to your car radio via aux inputs, or FM transmitter. You can buy a boombox for the home/work, or you can buy a home kit that will attach to your home stereo.
4. Yes, if you have the boombox
5. Not sure.
Also, XM is 9.99 a month, and additional units are 6.99. Keep in mind, a receiver=unit. Having a car kit and a boombox does not constitute as 2 units. ALSO, you must be near a window to use the boombox. Using it indoors with no windows around WILL NOT work, unless you get the MyFi which buffers 5 hours of music.
XM is also available online, and costs 3.99 a month if you have an XM account.
Thats all the info I have on XM. Sirius is 12.95 a month IIRC, has the NFL and Stern. XM has College football (ACC, Pac 10, big 10 so far). Sirius has college bball, i think. Either way, I don't think you will go wrong..hell, there was of a merger recently!