Welcome to the wonderful world of suspension! Your education will start now and end....... uh, never.
My first suggestion is to set the shocks to full soft for compression and rebound. I have found that often the shocks cause a harsh ride rather than the springs. Then adjust from there.
If you look at all of the Spec Boxster setups, you will see a surprisingly wide variety. For example, Topless' suggestion to help put the power down on turn exit is to run a softer spring (which is fine), however I like to run a softer rear roll bar to try to soften the rear end in corners. This not only lets me get the power down on turn exit but also to keep the rear end planted if there are bumps. At the end of my last race, I even had a fellow racer even get down on his hands and knees to see where my rear bar was set because he couldn't believe how well I was able to drive away from him in some corners. The trade off (yes, there is almost always a trade off) is that I give up some roll stiffness and have to account for the additional roll in my driving technique. Same goal, but different approaches for different drivers.
I will admit that I have no experience with the KW's and they might react completely differently than the PSS9's. With that being said, my next best suggestion is to find a local shop that is familiar with racing and have them help set up the car. There is a fine art in balancing shocks, springs, tires, ride height, rake, tire pressures, etc., and one size definitely does not fit all. Paying someone with the right experience to get the car into the ballpark as a starting point might save a lot of trial and error ($$$) in the long run. Then you can work the fine adjustments on your own and always go back to the baseline.