Let's think about this - 2 drivers, 2 SUV's, a 335i on order, plus you're contemplating a 4th vehicle. Evidently money is not much of a deciding factor for you. If it makes you feel good, then do it.

Driving a Fusion would feel the same as driving a rental car. The only thing missing would be the Avis sticker on the rear bumper. The VW is okay, but why not get the GLI? Same with the Mazda - why not get the 3S? It's not like you can't afford it.

While we're at it, how's about a Mini Cooper S or a Civic SI? Or better yet, a Lotus Exige?

If gas consumption reduction is all you're really chasing, then get an electric car, a hybrid, or a Honda NGV.