Hi. car has 127k on original struts/shocks, springs, 19" wheels. going over minor or major bumps felt just like that. did not bottom out but felt clunky. Bilstein B4 stuts/shocks are being advertised as fitting my car, and was looking at B4, B6, B8. goal was to maintain same car height.
Contacted Bilstein:
[soq]
There are no B4 series shocks available for this vehicle. The B8 is the only available shock directly compatible with this vehicle.
This is due to the springs for the S5 essentially acting as a lowering spring for the A5. Ride height is determined by the spring forces used to support the vehicle, a shock absorbers primary function is to control the spring force and resist drastic suspension inputs.
Installing this shock with the OEM spring would not be expected to change the ride height, Installing a B4 for an A5 however will increase the ride height and is not recommended. The B8 in this circumstance should offer a similar ride height to stock if utilizing OEM springs and will be slightly stiffer than the OEM shock as it is a performance oriented series.
[eoq]

Installed (from fcpeuro):
Audi Shock Kit - Bilstein B8 Performance Plus 24145985KT10
(B8 Performance Plus 24-145985, with sports suspension; without electronic suspension control, which matches my car)

Result: front and rear ride height unchanged. bumps have been smoothed out for sure.