I just did this. The Sirius antenna was different. The one I have has a connector for the Kenwood. I don't use, so didn't care. You would need to either get a Fusion connector model or splice a connector in to the antenna.
The connectors on the Fusion are different, but they provide pig tails so you just wire it in (use crimps, liquid plastic and tape on connection points). Very easy install.
I did the 650 black and white display. I changed out the 6" speakers in the helm with the Fusion 6" model, left the 4" Kenwoods down below. The Fusion speakers are superior and the cones on the Kenwoods were fraying - so good to do those speakers that are outside and see the elements.
The hardest part was fishing the wire from the helm to the head unit for the remote interface. I was able to do it with a fish tape and snake it through under the headliner. Take your time, it can be done. Took less than 3H to do the whole job. I really like the Fusion unit. I'm considering an amp and a 3rd set of speakers. The head unit has 2 channels for 4 speakers. If you want more than that, suggest you get an external amp. I'm thinking another set of 6" speakers where the cockpit lights are on the Marlin (GW installs there on the new boats) and moving the cockpit lights so I still have them. Highly recommend the unit from a environmental view. My Kenwood was inside the cabin and I could not believe the rust and tarnish on the metal and circuit board. Put in a Fusion and I think you'll be set for the life of the boat.
