I replaced my DRC - probably about 5 years or so ago and went with the Koni FSD inserts, and replaced all the rubber components and bushings, etc while in there. I did the work myself - it was a considerable job, especially not having access to a hoist. I looked into a complete coil over replacement (from all the available options). I did not want to lower the ride height and really did not want to stiffen up the ride and also really did not want to spend $2K+. I drive the car daily (no tracking). I have been very pleased with the decision. If you do research you will probably see that the Koni's will not be a fit for the RS6, but will for the A6 - 4.2 with sport suspension. It's because the RS6 has the DRC system, and obviously any aftermarket insert will not connect to the DRC's pressurized set-up. Everything went together fine - definitely will need coil compressors and air impact tool, torque tool etc. - the rears were much more difficult to remove than the fronts. I believe I picked up the Koni's for around $750 and then another $200 or so for the other OEM components.

Good Luck