My experience: I had tried a 400 disc Sony 555ES, and even brought it back and tried a second one, only to return that one too.
They sounded like dreck compared to the Sony 9ES 5 disc changer, even the 5 disc 7ES is wayyyy better.
(I own both a 7ES and a 9ES 5 disc changers, and used to have a Sony 89ES 5 disc that played endlessly for 8 years... I mean 12 hours a day, every day!)
Even using an Adcom DAC (which sounds as good decoding the output from the SCD777ES as the CD RCA out from my Sony SCD777ES) The 400 disc changer was total bad bad sound.
Those mega changers spend the money on bells and whistles, and skimp on the basics.
A compromise would be a used Sony 9ES 5 disc changer... good sound and still have a 5 disc changer.