My friend has decided to purchase an mp3 car entertainment system, but needs some advice on the way to proceed. He used to own a Sony MD changer which was fitted to his Honda Goldwing and still has the unit, so has some knowledge about in car audio systems. He has been advised Mp3 is the way to go, but needs a place to start, a hard drive based system is preferable to a USB storage system. Can someone advise on , the head unit, HD storage sizes available, and if the MD changer can be integrated as well, it is a Sony MD65 changer. It will be getting fitted to a G reg BMW 5series,the previous owner appeared to have had an entertainment system, as the wiring and "decent speakers" were left in the car. Any advice or websites that could help is gratefully appreciated.