Thank you Frank,
Your case is unusual. Usually,owners want to buy larger diameter wheels, because ‘they look better’!
Ride quality is obviously important to you ( and would be to me), but in effect, you have bought the wrong car by buying an S.Line, which has inherently harder suspension. My money would be on the likelihood that you bought the car on ‘looks and toys’, which Audi translate into ‘owner also wants roadholding at the expense of ride quality’.
One other factor to consider is whether your current tyres are extra load (XL), since if so, this will aggravate the already harsh ride.
Please let us know.