I'm heavily considering stepping down from the stock 245/45r20s to a 255/55r18 (which will require finding wheels I like, which is very challenging). Trouble with that is I am getting conflicting accounts from people online. One guy with a Charger/Challenger/300 will say that he "upgraded" from 18s to 20s and didn't feel any difference in ride, while another will say they test drove both and noticed a big difference. I think it's more of a difference in the drivers than the setups. Some people are completely oblivious, while others are very sensitive (like me). It's hard to justify the thousands of dollars involved in a wheel/tire change on the hope that the difference will be significant enough to solve the problem. I'm 100% sure there will be some improvement with a little more sidewall, but with no quantitative way to analyze it (and no spare wheels/tire to test before buying) I just can't know HOW MUCH difference it will make. I mean think about it, my old truck has 70 series tires on it and still managed to ride firm because it has a firm suspension meant for doing work. Tall tire doesn't automatically mean soft ride.
Really that's the entire issue here. Any of these changes require substantial financial investment with no clear evidence ahead of time that they will be sufficient to fix the ride quality to my standard. Also, if I drop 2 grand in wheels/tires going down to 18s, and the ride isn't fixed, that money is totally wasted because the car will sell for more with 20s on it.