For reference, I have the Eibach Pro Kit springs on my Z4 with MSport shocks, 18" Rims with NON Runflats and the ride is really nice.
I also have the Eibach's and MSport shocks on my E91 Touring with similar tyre & wheel combo and again the ride is spot on.
The Mini has the JCW shocks with the Eibach pro kit, 18" JCW rims with non-runflat tyres and is a little bit harsh on really bad roads but even using it daily its perfectly comfortable.
I guess my point is, 3 different cars but essentially the same spring/shock/tyre & wheel combination on them all and don't have any issue with ride quality.