I also have a 496, which has been serving me well for 18 months. I think its Automotive mode is poor. The need to have the speaker on a string thing plugged into the 12v socket on the car to get voice alerts is a nuisance. For aviation though, I'm quite happy with it.
I have a collection of other Garmins for other purposes; GPS Maps 60, 60CSx, 76C and a Street Pilot c510 for the car. They all work well but it's very expensive updating all those maps.
The Aera 550 would be nice. It could be used in the car as it has superior features to my c510. The 496's Automotive mode is no better than the 60/76 hand held series.
I don't think I can justify it though :-(