A few years ago I had a C5 A6 (FWD) with 17" wheels. I hired snow chains for a ski trip from Roofbox.co.uk. The only chains they were prepared to offer for an Audi were the Spikes-Spider ones because of clearance issues behind the wheel. The advantage of these were that, because you fit a plate to the wheel in advance, they are quick to fit and the plate helps to protect the alloy wheel both from kerbs and pot holes and also from the chain rubbing against the rim. I have no direct experience of using chains on a quattro but I am led to believe that firstly you are likely to have even less need to fit them in marginal conditions but if the sign says they must be fitted then so be it and that you only need them on the front wheels as you would if the car were FWD.
Have a good trip