Upgrade Help: CDP or DAC

I think you will really be better off with a tubed DAC if your goal is to reduce listener fatigue caused by harsh upper mids and highs. But be careful. Unit selection and tube selection is very important to achieve this. Out of the box a tube unit can sound just as bright and fatiguing as a SS one. The essential difference is that you can change a tubed DAC's sound by simply changing the tube(s).

A recommendation - find a used California Audio Alpha or Sigma DAC and play with it and your Marantz. Be prepared to change tubes a bit. I have used both - the Sigma is cheaper and for all pratical purposes just as good as the Alpha. It only has one tube too. I presently have one set up with a Cal Delta transport in my Headphone system. I found that it sounds best with a JJ 12AX7 (an inexpensive new production tube). Compared to my Marantz SA11S3 this is warmer in tone and certainly not fatiguing at all. You could probably find the Sigma for sale on A-Gon, if you are patient, for $200, and better yet you could probably get it with a matching Delta transport for less than $500. And if you don't like it it should be easy to resell. They are still popular.

On a side note, you should also research cables in the archives. You'll need a Toslink (optical) cable from CDP to DAC input.
Try not to let all the different opinions in the threads drive you crazy. You don't need to spend big bucks for a decent cable.

Definitely go for a DAC, and if you're looking for a warmer, more musical sound, then I'd suggest you try the Rega DAC, which you can find used for $700 or less. I have tried a number of DACs and I find the Rega is one of the most non-fatiguing around.

PS -- following up on my suggestion of the Rega DAC -- I personally prefer it to tube DACs I've tried (including CAL) -- quieter background, no worries about tube rolling.

Your Marantz 5004 player has coaxial digital output. Contrary to what Lowrider says, I think you should use coaxial, not optical. But I agree that you don't need an expensive cable. You need a true 75-ohm cable. Best best is a digital cable from Blue Jeans Cable. Well-made, no nonsense, fine sound.

Yes, I meant to include the coax output; it is the preferred connection from transport to DAC. Momentary lapse.