2008 Audi A6 4.2 quattro 4dr Sedan AWD (4.2L 8cyl 6A)
I sold my M3 because my kids were getting too big for the back seat and my wife couldn't drive a stick. I owned a 2004 Allroad at one point and loved it so I thought it'd be cool to come back to Audi. Well, now it's three weeks later and I just sold it for a BMW 535. The seats, while nice, offer very little support when going through hard turns. The headroom is terrible - I'm 6' 3" and my hair brushed the headliner every time. The car is very smooth - almost too smooth. I felt like I was driving a luxury yacht. Performance of the V8 is pretty good and with good mileage. If you like to float in luxury, this is your car, but if you're looking for a little better driving experience, pass.
V8, interior design (no one, but no one beats an Audi interior), MMI easy to figure out quickly and use, center dashboard display (vs. always having to look at the MMI screen). Bose Surround is very nice.
Tighten up the suspension on the base model. Beef up the seats and make them more adjustable. Shrink and fatten the steering wheel so you don't feel like you're steering the Titanic.