A nice suggestion. The A8 is pretty, has the requisite panache (without being over the top), and is well made. The Jeep idea died when I read the reports about road noise and squeaks. I drive the highways so it would not work out. Also, I'm still not quite there with American cars.
As for the weekend car, I would worry about legroom in the Boxster, but I hear where your going with that . . .