I put my music on my phone and bought a jabra 700 blurtooth speaker kit. It pairs with the fm radio and my phone plays the music out of the car stereo. Pretty sweet and simple. Nothing to install, just turn the radio to the station the unit tells you to. In my car it is 88.1 fm.

The Blackberry Storm can get pandora and Rhapsody, you could play them thru the existing stereo if you want.