I went from a standard 16 bit (it may have been 18 bit) 506 to 596 and the 596 was much better but I would have expected that. I soon upgraded to 598 spec though where DVD-A was sublime.
What I did not appreciate was that I am inherrintly lazy so I leave my last CD in the player (DVD's for some reason normally take out once I finished watching them). Thus, sharing CD and DVD in a single player came as a bit of a shock, until I got my squeezebox where I have 400 CD's on tap at the press of a few buttons.
If you don't already frequent the area, may be worth searching the
unofficial Meridian website. You will find plenty of opinions there.