[Kreisler jr]

Classical is mixed and mastered quite differently from rock, jazz, etc. Most notably, classical isn't nearly so low-end focused. Far fewer early digital recordings, or CD transfers of classical sounded bad. Thus didn't/don't require remaster after remaster after remaster.

I pretty much gave up on getting new remasterings. While I think that there were a bunch of 1980s CDs that were improved by later remasterings, the results are usually subtle. I distinctly remember two famous recordings where I found a newer remastering clearly superior to a late 1980s CD issue, the Callas/De Sabata Tosca and Klemp's Brahms Requiem. I also think that some CBS CDs of their 60s recordings (before it was taken by Sony) in the late 1980s sounded quite bad, e.g. some of Casadesus/Szell Mozart. The Gould recordings sounded different as well between CBS and Sony but I am not sure which ones sounded better.
I eventually also got more recent issues of some Mahler and Beethoven's Fidelio with Klemperer. I pretty much gave up, however, when I was completely unable to decide in case of some other recordings which one I preferred, one was, I think Furtwängler's Haydn #88 and Schumann #4, another might have been some Fricsay or again Klemperer/EMI because in A-B-comparison I could perceive slight differences but was totally unable to decide which one were sounding better to me.

If a recording from the stereo or digital age was pretty good in the first place and well transferred to CD there are almost no improvements to be had by further remastering, I think.

 

[Kreisler jr]

Are these the cheap "white" cardboard boxes from Sony? Or some "original cover art" boxes?
Of the cheapo "white boxes" I have Levine/Mahler, Walter/Mahler, Szell/Haydn, Leinsdorf/Prokofiev and Serkin/Beethoven and didn't notice any particularly problematic sound, i.e. nothing that would be surprising or very substandard for ca. 1960s recordings (never known for especially good sound, unlike some Mercury or Decca).
However, I could only have made comparison in one or two cases (Walter/Mahler and Serkin) and I didn't really before giving away the older single issues. I am not that particular about sound, though