Improvements of Modwright Sony 9100ES over 999ES?

is it worth going to the 9100ES Modwright Sony from the 999ES Modwright Sony CD Players? What improvements would I hear? Has anybody upgraded and can talk about it? Thanks.
I was wondering the same thing. I also have a modwright 999ES. Did others upgrade to the 9100ES or go a different route?
I have an un-Modright 999ES. What mods did Modright do to the 999 and what did it cost?