I test drove a 57 plate A6 Avant 3.0 TDI Quatro Auto with 40k miles on it about 18 months ago and was entirely unimpressed.
It wasn’t nasty or objectionable in any way but it just left me cold, couldn’t get excited about it in any way. It wasn’t particularly quick, comfy, nice to look at (IMO) and didn’t handle particularly well either although in all fairness it wasn’t particularly bad at any of those things either. As a driving experience and for overall comfort I much preferred the 2.0 TDCI focus with 100k on the clock that I had at the time.
Also, the driver’s seat was very wide in spite of it being allegedly a “sports” seat there was acres of space between me and the sides of the seat so I slid about the seat a bit going round even gentle corners, I guess the average A6 driver must have considerably more than a 32″ waist 😉