My wife and I had the same conundrum when we were looking for my car.
I wanted a fun car for a change which handled like a dream. The size of the rear seating was one of the requirements, as well as Navigation and other safety and usability features.
The BMW, Audi and Passat ended up on the short list. Didn't consider the Volvo because I didn't care much for the styling. Mercedes has a bad rep for reliability, so it was also eliminated. The Acura was out due to the terrible handling and turning radius. The Lexus ES330 wasn't my cup of tea.
The BMW 3 series was too small in the rear, and moving up to the 5 had a bigger interior, but the cost with options shot up way over $50K.
The Audi A4 looked nice, but also had inadequate rear seating - and hence, eliminated. Given the pricing for the A6, that was also eliminated.
The v6 Passat fit the bill for us. A really fun car to drive, and when fully loaded, can be had for less than $35K!
At that price, many will question why I would pay an entry-lux price for a non-luxury brand. In my opinion, I paid for the car I LOVE to drive, not the brand.
The Audi and BMW may invariably have better appointments and handling compared to the Passat, but the 40% increase in cost doesn't justify the 10% increase in performance.
For those who can afford such a cost, more power to you.