I have a Marantz CD 52 MK2 connected to a more vintage second hifi which is 33yrs old only ever needing the common fault of the eject cog replacing after it literally perished.
I've been upgrading, swapping, demoing etc etc like a lot on here for a long time being bitten by the bug thus never staying still too long found the only real noticeable upgrade I could find within bracket was a newer marantz CD 60 after many a demo and having all sorts in-between.
The main impact in sound is given primarily by the speakers then the amp.
Given the other ancillaries like the CDP etc is of a decent good "similar" quality it becomes harder to both find much difference and then improve on without large jumps in price.
Even then I find it's more where system "tweaking" comes into play by making the subtle changes to your overall sound that make a system uniquely to your taste.
I'm not sure if you will hear much difference in sound but I will vouch for Marantz being very good quality.