I saw two 2005 A6's at my local dealer last week, but they were Canadian spec, just passing through the Port of Houston. One was a 3.1 V-6 with FSI, the other was a 4.2 V-8 w/o FSI.
I was allowed to sit in the cars, but not to drive. The increased overall size impressed me, and the interior not unlike the new A8. The MMI is easier to use, and has a nice color screen that is always visible, unlike the pop-up screen in the A8. Both cars had very comfortable and supportive sport seats. The trunk is huge, bigger than the A8. Rear seat room is much improved for six-footers like me. CD changer is in the glove compartment; phone is in the armrest, and is detachable.
The 4.2 had 18" wheels like on the new A8, and the 3.1 had 17" wheels. It looks better with the 18 inchers.
As for the new grille, it looks much better in the flesh than in photos, and I don't find it offensive as some do. It's merely an evolution of the old twin grills into a single, large grill.
I was told the 4.2 with all options will be around $56K, while the 3.1 is in the 40's. I am also told that 4.2's will be rare!