I recently acquired a used (but in a pristine condition) box set of the Japanese single-layered SACD box set of Bernstein's first Mahler cycle, and my heaven, this is a BLAST!
The remastered sound (which apparently originates from the same source as Sony's remastered CD set) heard on these discs is REVELATION. Furthermore, each symphony is contained on a single disc so I don't have to switch the discs! It all comes in 9 discs.
The sound is much cleaner and clearer with no hint of tape dropouts or saturation, and the dynamic range has improved substantially too. I can hear all the nitty gritty details that were audible only vaguely (even on the Japanese hybrid SACDs) and now the listening experience comes closest to listening to LPs minus surface noises.
It is pricy (close to or over $200) but by all means, get the set if you can.
John