spend on the streamer or on the DAC ?

In this setup my Node2 does the full MQA unfolding before sending it to the DAC (via digital coax).

Actually, no.  You only get the full unfold if you send output to the analog outs of the Node 2.

https://support1.bluesound.com/hc/en-us/community/posts/360037876633-MQA-Confusion

I have yet to see a technical reason as to why the streamer does or doesn't matter, but my experience was that an external DAC did improve sound quality (in my case an Auralic Vega), but that replacing the Node 2 with a higher end streamer/DAC (for me it was the TEAC NT-505) resulted in a greater improvement in sound quality, a less "digital" sound, and a larger more "holographic" soundstage.  As others have said, the app you use to control your streaming is also important.

One point that seems to be getting lost in the conversation is how your streamer is connected to the internet. I noticed a huge difference in all aspects of the sound after I ran a direct wired connection to my streamer. Wireless is convenient but igo with the direct connection when ever you can. I also added an IFi filter on the connection and it cleaned up the jitter and noise.

Thk u all for the useful insights. I  am attracted to a single-box solution (streamer/DAC, and I'd like to
keep my MOON amp,and MOON seems to make nice DAC/streamers BTW). In this regard there is the issue of obsolescence: where does technology move the fastest, on the streamer side or on the DAC side? This might be an issue if one considers future upgrades. Regards. Olivier

I am waiting for a Denafrips Pontus DAC to arrive and I will team that up with a Bluesound Node 2i streamer for the time being. Read the reviews on the Denafrips as they read to be an excellent performer. 

Bill from Nova Scotia

I’m fairly new to this game and have to say my dealer recommended I go to Linn and solve both ends of this question. I ended up buying the Linn Maljik dsm and have been very happy with the streamer and dac contained in this unit.