[nmpriusman]

Although this option is more expensive than getting the XM at Bestbuy, Coastaletech.com has a wonderful XM satalite radio option for the 2004 Prius. It is actually integrated into the LCD screen, so you don't have the little device that you have to leave somewhere on the dash. It costs $410, but it could be worth the price in terms of utility and looks.

http://www.coastaletech.com/xm_radio_in_prius.htm