Anyone thats looking for a coilover setup for their B5 S4 should be checking out the KONI coilover kit from Stasis engineering.
Stasis pre-sets the dampening which is a huge + because that is the hardest part in getting your car to ride right.
It also provides several different ride height adjustments and it rides awesome trust me, i have it installed on my S4 and its amazing.
If you wanna spend some serious money, Penske is where you wanna go.