The mod's DEFINITELY WORK. I have heard Richard Kern (audiomod.com) and Dan Wright (modwright.com) modifified scd-1 units and cannot recommend them enough. Both guys have great reputations.
I just bought a used richard kern modified audiocom scd-1. I still have my original scd-1 and a/b compare them. It's like the difference between a $500 Cd player and a $2000 CD player. I can't believe how much better it is. Much lower noise floor, truer instrument timbres, and the soundstage seems twice as wide. I don't think I've heard a lower noise floor. If I had known the level of improvement I would have had it done long ago.
A few weeks ago Dan Wright brought his Modwright XA777ES (the one from CES) with the tubed output stage to my house and it's unbelievable too. It also sounded much better than my stock scd-1. Had the glorious tube warmth to go with SACD's awesome resolution. It's also a great redbook player - better than the stock SCD-1.
I would guess that having a 9000 would probably be an even more dramatic improvement since it has lower component quality than the scd-1.