I agree with you in this point : A hardware upgrade-of mainboards or CPU would be nice.

For example :
I was told the SD1 (Ketron) uses a 64 voice DREAM/ALMATEL soundchip. DREAM already has a 256 voice-soundchip available including 256 Mb (!) flashrom inside.
The reason brands do not implement the very latest technology is 'costs' and not wanting to 'please' all customers so they have all they want.
It is a strategy to slow down the progress en launch a new model every 3 years, so they keep customers happy.

I myself am willing to put some extra money to upgrade or increase CPU power / memory / polyphony...... if available

Roel