Hi Graham.
Being a previous PA800 and E80 owner I think you will definitely like the E80 and get more out of this than the Korg
If you do fancy going for one of the expansion boards I didn't think the SRG-01 offered many good sounds. I have heard the latest piano board and brass in action and those 2 were far better. There's certainly enough expansions, styles and registrations out there for the E80 to keep you happy for many months to come.