Which DAC prevails in this chain of converters?

Only one DAC is active at a time, so you have 3 choices:

1) Run the analog out from your CD into an analog RCA input on your Marantz. Use the stand alone DAC as a paper weight. The DAC in your CD player is the only active DAC in this chain.

2) Run digital out from your CD player into a digital input on the Marantz, leave the stand-alone DAC atop the stack of paper. The DAC in the Marantz is the only active DAC in this chain.

3) Fetch the stand alone DAC from the papers. Run digital out of your CD player into the digital input on your stand alone DAC. Run the analog output from your DAC into an analog RCA input on your Marantz. The stand alone DAC is the only active DAC in this chain.

Compare the 3 options and choose the one you like best.

Good Luck

Marty

Are you asking, whether your CD player, DAC or receiver is actually converting the signal to analog? Or do you think that each one is doing the same thing in series? With each contributing to a refinement of the signal
Well to my knowledge it doesn't work as a series. The CD player will make the signal analog unless you bypass it's DAC and use digital outs. The DAC will not take an analog signal and convert it to digital then back to analog unless it specifically is capable of doing that. Instead I think it will just pass the analog signal along perhaps?? The analog/output stage of the DAC might get involved but I doubt it. The reciever will accept the analog signal as well and not convert it again, but, in this case the analog output stage will be involved in handling the signal and will matter in the final sound.
To answer your question the CD player.
If you are asking what you should invest in for upgrading. I think the one box CD player with the best transport mechanism, DAC and analog stage you can afford is the way to go.

Finally, the "piped to preamp" step, which is often neglected in reviews/previews/analysis of DACs. People sometimes go on and on and on about Wolfson this and Burr-Brown that, when it's this output stage here where we separate the men from the boys. Trebejo

In my view this is THE most significant stage in the process. I've come to this conclusion after trying to beat my old 20 bit cdp with newer, more sophisticated cdps. None of them come close and I believe it is the analog output stage that is the difference.

I agree with Trebejo. He has more patience than I do. ;)

Ok, you have not given any model numbers so I'll keep this nice and abstract.

digital info -> converted to analog signal -> piped to preamp

The "digital info" part is pretty much the same, modulo some considerations that I have a really, really hard time taking seriously. I might get flamed for this but it's getting really boring to reply to them.

The "converted to analog signal" is where real variations begin. Which DAC chip was used? How well was the circuit built around it? How about the DSP? Note that all the usual comments about the beauty of analog sound, avoiding silicon transistors, beautiful tube sound, etc. all bump up against this step here--as far as I know it is impossible to avoid using silicon transistors for this step. :)

Finally, the "piped to preamp" step, which is often neglected in reviews/previews/analysis of DACs. People sometimes go on and on and on about Wolfson this and Burr-Brown that, when it's this output stage here where we separate the men from the boys.

So going back to your original question, you'd have to look inside and see how each of those three devices implements each of the latter two stages. In principle, the DAC should do the best job, since its only function is to be a DAC! In practice, it depends on which models you are using.

I'll go out on a limb and claim that if the DAC does not sound better than the receiver or the CD player, then you either have a kickass receiver and CD player, or a mediocre DAC.

Unfortunately we do have a chain from source to speakers and if the preamp and amp and speakers are not up to snuff then the DAC's abilities may be unfairly obscured; so use the min-max principle, upgrade the weakest link in the chain and when you're sure that's the DAC, go for it and you won't be disappointed.

Only YOU can make that decision. Try it both ways, and see what YOU prefer.