I am not sure how much you can improve the SACD performance of the SONY C555ES. At the time of its release (2000), its SACD performance was rated an A+ by Stereophile.
Is your concern more about owning an aging SACD player that has reported problems with some of its moving parts and seems to be only repairable at SONY's Laredo facility? It's a legitimate concern ... I have the same one, as my SONY C555ES is now 8 years old.
What I did was to purchase a redbook CD player for most of my cd playing and to just use the SONY for SACD playing. In addition to my SONY, I own a Rega Apollo CD player and a Musical Fidelity CD Pre 24 (preamp/ cd player combo) that I rotate between two of my systems. The other equipment is a Prima Luna Prologue 5 tube amplifier and Opera Platea floorstanders.
When the SONY finally does go, I don't know if I will replace it with another SACD player. I own 300 or so SACD discs, but only a dozen or so SACD only discs. Yeah, there are differences between redbook and SACD, but not at a level that I get too worked up about.
For my $1500, I would look to purchase the best redbook player that you can that would work with your equipment ... Rega Apolllo, Cambridge Audio 840, Musical Fidelity A.5, or Naim.
Best regards,
Rich
