If you seriously only want Redbook 16/44 24/96 I would look at a used Esoteric CDP that uses a Multibit converter as they do pcm (redbook) better.
Like these: as these are Multibit Esoteric players
ESOTERIC X-10w / X-10WD
And the Naim CD5X you have is a very good redbook player as it is Multibit, my dream one is the Naim CD555 with 555PS power supply. I have a Linn CD12 MkIII (multibit) and that 555 Naim is the only one I would sub it for.
MoJo Music quote:
" When a PCM (redbook) file is played on a dsd, sacd or Bit Stream converter, the DAC chip has to convert the PCM to DSD in real time. This is one of the major reasons people claim DSD sounds better than PCM, when in fact, it is just that the chip in most modern single-bit delta sigma DACs do a poor job of decoding PCM.