I have a 1993 Euro Spec 318is and a 1997 US Spec 540i (with premium sound). What is the most compatible retro-fit/after market configuration that would allow me to connect my iPod (Nano 3rd gen) to my cars? I don't want an FM radio connection - I prefer a hard line where the iPod gets charged. Additionally, I don't care about seeing the display. I'd like to just start with a playlist and go - possibly use the iPod functions to skip or go back a track or two. I also don't mind changing the head units but prefer to keep them stock. Thanks.