I have the Alpine IVA-D901 and as one of the optional upgrades you can plug a device by Alpine into the radios seperate brain/control unit which gives a digital link up to the radio through a device called the KCA-420i I love it!!! Direct digital signal and I get to bring every peice of music I have along for the ride. I also just installed XM radio through direct digital inputs. I dont listen to the AM or FM anymore....Also this unit allows for the iPod to be controller from the radio....