Kung yung mismong aux input ng head unit yan, RCA yata dapat yung input. Depending on what your head unit is, you can buy an adapter that will allow you to plug any MP3 player into that aux in.
I had an RB10 attached to my pioneer head unit before. Tapos I just bought a baby plug to RCA cable para I can connect my iPod or my friends' MP3 players to my car audio.