I've read people on here saying that the non-sport package (no adaptive drive) ends up actually being a rougher ride. I have a 4.8i with sport package and 20" wheels and have been very pleasantly surprised at how smooth the car rides with a sport suspension and low profile tires. Handles bumps much smoother than other cars I've owned and driven with similar profile tires and sport suspensions.

If you haven't already, I would suggest driving both setups (20" wheels with and without sport package) and then decide.