The suspension on the A4 is a fun one when it goes wrong. The bushes are made out of piss or something as equally rubbish, so they fail and when one goes they all go. You can buy the parts in singles, but you really want to change them all at the same time, or your car will be in and out of the garage for months.
They are a bit of a faff at times to get to some of the bolts, but they aren't that hard to work on.