Hi Esh,
You are right that your Kurzweil PC88 (and my Fatar 1176 as well) keyboards both have 'fully weighted' piano action while the 9000pro has synth action. Coming from a background as an acoustic piano player myself, I fully understand your fustrations in adjusting to the synth action of the 9000. It took me a while to ajust from my 'heavier than typical' weighted action acoustic Steinway to a synth action (no weight) keyboard, but now that I have adjusted, I can now easily switch back and worth. When purchased my first synth arranger (Technics KN5000), I thought I'd never adapt, but keep the faith, in time you'll be glad you persisted in working to adjust your playing style & technique to adapt to synth keys. Your back will thank you for it, if and when you have to move it.

Scott