I think you are answering your own question. If you don't plan to take FP90 to gigs, and you have a good discount on it, the FP90 is appealing all the more. I tried out the RD2000 at NAMM. It is becoming more like a workstaion with many sounds and features rather than a stage piano. More expensive, too. Overall, I'd choose the FP90. The onboard speakers will come in handy, too. The weight of the FP90 action would be very similar to your Casio, not too heavy nor too light.