Are you saying a 200 lb/in spring can be tuned to give the same ride as a 145 lb/in spring with dampening alone? Or are you saying that the only purpose of different spring rates is to set ride height?
Yes.
The better question to ask is what perceivable difference in ride is there between those two springs, assuming the ride height is the same with both.
Just so you know, I've played with rates with a similar variance to the ones you are suggesting.