I have a brand new I IV for sale. It's a nice system but I've gone another way. Here's the unit on J&M's website.
http://www.jmcorp.com/SeeProducts.asp?PF=29
It's a pretty cool deal, you can hook up several different units (2 way radio, cell, mp3, gps, etc) to it and it'll even power a radar detector. I'll let it go for $50 plus shipping or best offer. Let me know.