There is a flaw with the Marantz DV6400s software. (1) Certain hybrid SACDs (and perhaps pure SACDs, but I don't have any to test) force the set-up software in the Marantz DV6400 to change the SACD setting from SACD-->MULTI-CH to SACD-->2 CH. Thus, hybrid SACDs that should be playing in 5.1 only play in 2 channel. (2) The set-up software will hold this SACD-->2 CH setting afterwards (regardless of what SACD is playing) until you physically go into the set-up menu and change the setting back to SACD-->MULTI-CH. Of course, if an "offending" hybrid SACD is in the Marantz, the DV6400 will shift back to SACD-->2 CH, so you can only make the change back to SACD-->MULTI-CH when the 6400 is either empty or has a "non-offending" hybrid SACD inserted. (3) I only have 6 hybrid SACDs (and no pure SACCDs), so my testing is limited. The following hybrid SACDs exhibit this problem, "The Freewheelin' Bob Dylan" (2003 remaster), Bob Dylan's "Oh Mercy" (2003 remaster), and Bob Dylan's "John Wesley Harding" (2003 remaster). My other hybrid SACDs (including two from the 2003 Dylan remastered series) seem to work fine and do not force the set-up settings to change. (4) My local Marantz dealer has already swapped out my original DV6400, and I can reproduce this problem on the new 6400 I've received from the dealer. I initially contacted Marantz three weeks ago. Five phone calls (from me) later, I was told by the technical support guy that they couldn't help and they would let an engineer know about the trouble.