Audi RS6 is a real hero now. Specially on North American market because fast wagons are rare in this region. But RS6 has a practice not worse than some Ford Explorer or other SUV with the same size. And by the way new A6 Avant in C8-body is really pretty car.
Even if some BMW and Mercedes will a little faster, it's still will be a fantastic and practice car. And be sure - nobody will think that you are uncool because drive wagon.