The DCD-3520 used PCM64P dacs and a KSS-151A laser. both of these highly rated today and rare and expensive to buy.
For Redbook replay you would be hard pressed to find a better d/a converter than the R2R Lader Multibit PCM63K.
R2R multibit is the only way to convert PCM Redbook "bit perfect".
All these newer DSD types, bitstream,1bit, ESS Sabre ect are not as good for Redbook as R2R is.
This is why you find all the big heavy hitters MSB, Trinity, ect, going back to R2R for PCM Redbook conversion
To make the Denon DCD3520 into a absolute giant killer for Redbook, you’ll need to get someone good with mods, to bring the I/V stage and output buffers up to date. This could cost a couple of hundred bucks.
Cheers George