Streaming through upconverting DAC - can I even improve audio quality?

You really would benefit by ditching Spotify and subscribing to Qobuz. That alone will provide a very noticeable change in how you’re hearing things.

Thanks, I'll give Qobuz a try first.  I'm trying to compare streaming to music I know well that I play on CD or SACD which is the only way I can judge.  I guess I don't understand if any signal the stream outputs is getting upsampled and upconverted to 11.2 what difference it makes as to what signal is streamed as input.  I'm sure the answer is technical and I'd be surprised if everything doesn't make a difference.  More experimentation is certainly in order.  Trying to find the sweet spot bang for the buck.  

But here's the thing:  so far, just using free Spotify 44.1 redbook quality,

Where did you get that info? It's totally incorrect. Spotify doesn't offer any redbook ouput. They have nothing but lossy streaming at a max of 320kbs. And the free service tops out at 160kbs when streaming.

Tidal, Qobuz, Amazon, Apple and others offer 16/44.1 which is REDBOOK CD quality in lossless formats.

Yes, better streamers and better DACs will sound better but you really need a better streaming service to make that a reality.

The 44.1 redbook quality I am referring to is the sampling frequency of the linear PCM signal input to the Marantz DAC.  That's what the Marantz manual says.  What I'm hearing sounds as good as CD but of course the Marantz is upsampling.  Maybe the 44.1 is a default number since that's the lowest frequency supported by the Marantz and what's happening is the Marantz is upsampling and converting Spotify's 160kb signal.  I've never been able to find any really good review on the Marantz DAC when streaming through its coax input.

@eisen0169 

I’m not really big on the upsampling thought process as I believe that if the gear can’t reproduce 16/24/32 bit audio in the first place there’s no point in worrying higher sampling rates.

So much of this depends upon the design and build quality of each component as well. From what I’ve read in your first post I would start with comparisons between your SACD players output and how that compares to streaming content. If you’re playing CD’s this will be more of an apple to apples comparison. Note the differences of what you like or not and start your focus there.

I use a Naim Uniti Core to store/playback my CD’s. I have a lower model Lumin U2 Mini transport for streaming. Although I listen to the music through the Lumin almost everyday I still prefer the sound of the ripped CD from the Naim- regardless of what format or sample rate the Lumin is streaming the music in. I run the Lumin native- even though it will upsample to 512 or something crazy it’s always playing the file in its native format.

My point with this to start simple and work with what you have from a basic level rather than being lured into what seems to be greater features. You may find in the end that they really don’t perform with that great of a difference or that the gear you’re using isn’t really that good at performing them anyway. If you start with a basic comparison- CD player 16/44 Redbook through your chain vs streaming 16/44 through your chain you’re able to analyze the difference. Use that a while and get comfortable before moving up to comparing CD against upsampled streaming content. You may find that those features aren’t really that important to you and if they do turn out to be at least you’ll have invested the time into discovering the nuances between both. Have fun and enjoy!