I can't speak for the Pioneer but I know the Alpine's will work with some hard drives. You just need to power up the external enclosure if need be. What is much easier is to use a thumb drive. With the Alpine's that have a USB port you can just plug your thumb drive into it and it will scan the folders for music. A head unit like the iDA-x100 gives you the best control over your music and folders. The Alpine head units also work with just about anything that uses MTP, so you could use a Zen or another device too. Pretty much the Zune is the one portable media player that doesn't work with anything yet.