I'm having a hard time deciding between the $800 Nav IV and the $650 Zumo 660. My 12 1200RT bike already has the factory XM so I don't need anything like the 665 either. The Nav IV will cost more and I don't know if the added cost will yield me any more benefits over the 660, especially since the screen size is the same. Plus, I don't see me wanting to worry about pairing with a cell phone as I'm not that important that I need to be in constant contact with anyone. Does anybody have experience with either or both of them? Thanks.