I had NO idea there was an Audi Club at Chase Field. I tend to always get a seat on the lower level, somewhere between home and 1st or home and 3rd. I went to the July 5th game, mainly for the fireworks. The game was sold out for that, although I managed to get a ticket at the last minute in a 200-section on the first row -- awesome seat!
I had to go through the Audi Club to get there - very cool! It's enclosed (air conditioning!) and has great bathrooms. There's Audi advertising throughout (to be expected) and even a real car on display! There's a cool Audi bar with a great view of the field, and a few fast food joints. One was a burger joint at which I stood in line for a long time for a burger. It wasn't too bad for ballpark food, but they really need to do a better job of line queue organization. I ate in a nice section of table and chairs near the Audi car. This eating area has great TVs to watch the game while you're away from your seat.
The hallways are interior, unlike the wide open concourses on the lower and upper levels. Regular sized doors are the opening to your seating section. I found mine and had a great time at the game -- great seat!
Full disclosure: I drive and love Audis.