Has your mechanic checked the condition of the shocks/struts yet? If not, simple check you can do yourself. push down on each corner. It should go down, rebound back up and settle. If it goes down again and back up, then have them replaced.
If ok, all you can do is beef up the suspension by upgrading the shocks/struts to start with. I personally would go with Bilstein for your Audi. They give a superior ride for performance and luxury cars.
After that, if still needing some more beefing up, have your mechanic change out the cotnrol arm bushings, especially if yours are still original. 15yrs old, they will dry and shrink some, which can be just enough to degrade the quality of the ride so that you do feel the bumps and potholes much more.