A friend of mine had a 90 Quattro a few years back, handling was awsome, acceleration was also good but parts were/are very expensive. I suggest a call to the parts department about common items and see for yourself. For the V6 they always replace the waterpump when they replace the timig belt (it has a belt so it is necessary around 60k) and it ain't cheap. For a while I was toying with the idea of getting an A6 but common parts (brake pads, hoses, filters, etc) are so much more expensive than for the 124/201, I stuck with the Benz.

Alex