I have the Zaon interfaced to our 550 and it works a treat. I also have the 550 voice interfaced to a spare input on the GMA340 audio panel so you get voice warnings (traffic / terrain / altitude etc...) from the GPS through the intercom.
I have all powered from the a/c power, and a hull mounted antenna next to the 430W antenna, with all the cabling hidden behind the dash. It is seriously good bit of kit as a budget traffic detector and works well, especially at close range, and I think it makes me visually acquire far more traffic than I would have had I not had it.