I paid to have an audio shop do the install, but I told them the Premium system was unpowered so they would not need a line out converter, and to remove the factory amp. I have installed stereos before, but I paid to have this done because they built a custom sub box in the trunk so it would not take up a lot of room, and I wanted it to be done right. I was not familiar with the Honda's differential balanced outputs, so I didn't want to mess anything up. I also wanted the tweeters done right in the factory A-pillars, so I knew a shop would have experience doing the work. I did not have the time to tackle the job myself, even though I would have enjoyed doing it. I posted photos of the installation with a PDF of the wiring diagram for the Navi system with Premium, and the external amp. So that should help you. The PDF link is at the bottom of the post after the pics. The shop told me the wiring diagram was accurate and made their job easier to do.
