Miden,

Manuel Dorantes lives in Arizona...

Speaking of your problem, I REALLY think that you should sit down and let the present feeling of frustration fade away.
The SD1 is still an excellent arranger and if you take the time to accustom with it you will be rewarded by what you will receive in return.
Thinking of replacing the keybed is just plain unfeasible; besides, it would cost you much more money and the results are simply non-predictable.
I understand how you feel now but, having owned an SD1 in the past, I can tell you that you own an excellent keyboard (just ask Donny for a confirmation...)
Thinking of swapping the SD1 for a Midjay, with all the due respect for a Midjay, goes to prove that right now you are in an altered state of mind, which leads you to perceive things in a rather distorted way.
(No offense implied, just a plain constatation... )
So my advice is: sit down, try to calm, play your SD1 more and then make up your mind.