From what I understood Stam is considering a Second keyboard for use next to his PA-80,
NOT as a back-up. If that is correct the purchase of a PA-50 would be very unwise, what is the point in a virtually identical keyboard ?
If the PSR3000 is a bit too expensive you might consider another PSR (2100, 2000), the new budget Roland (GW7), a decent secondhand Technics (the KN6000 comes to mind) or a Ketron/Solton , second-hand.

regards,
john