OK, Streamers: "Head" units only...?

You have several options here.  You might consider the Lumin U1 mini (within your budget) or the Auralic Aries G1 (also w/in your budget).  Both are just streamers and both should be a significant upgrade over the Node 2’s streaming quality.  I auditioned the Lumin mini and own the Auralic Aries G2 as well as a Node 2 in one of my systems.  But, the G1 should also be a nice improvement too.  And, both units will play well with Qobus, Tidal, Spotify and other services.  If you have a decent DAC, improving the streamer is a nice and easy way to get a big improvement.  At least in my experience. YMMV.

Best,
mgrif

OP here... ;-)
I think the progression of head only, or close to it, could go something like this:

1. Google Chromecast...$35
2. Apple APE then Apple TV...~$75
3. Sonos Connect...$350
4. Bluesound Node 2i...$5005. Project Streambox...$800 or so
6. Roon Nucleus...$1,400
7. Bryston BDP?....$1,400
8. Lumin U1 mini...$2,000

I know there are are a ton of products in the $1200 - $2,400 range and this is by no means comprehensive. There’s also the DIY world of raspberry Pi or something and also implementations of it like Project but that’s ain’t for me.

But, as one goes up market and still ONLY wants to stream a signal that goes to our existing DAC, I still want to know what we get SQ-wise what is gained going from, as an example, a Bluesound to a Lumin.
We get that the app is also crucial and a separate thread is addressing that now.
Sure, a home audition can help. But, what am I looking for.. and why is it better if we spend more?

or, are we fine with our nodes?
and, yes, I have a good dac.

I think the Bluesound Node occupies something of a sweet spot in terms of value for your audiophile dollar. The Blu OS interface is first rate and the Bluesound folks do a good job of keeping it up to date.  Add a decent external DAC and you are off to the races. That being said, both the SQ and the interface can be bettered, but you pay a premium for that extra bit of goodness, and the scale is sort of logarithmic.  At almost $2100 including lifetime subscription do I think Roon Nucleus is 3 or 4 times better than a $550 Bluesound Node 2i.  No I do not.  Do I think it is worth the premium.  Yes I do.  In my opinion the ride is worth the fare.  But that is very much an individual decision.   

A couple more dedicated streamers:

Bel Canto e.One Stream - $1595
SimAudio Moon Mind2 - $1900
DCS Network Bridge - $4750

Last summer, I had reached out to the designer/owner of my dac (Mojo Mystique v3) to ask a question about the outputs. He asked about my source, and when I mentioned that I was using a modded Sonos Connect, he replied that I was only getting probably 40% of his DAC’s capabilities.

Thus started a long conversation on digital servers, streamers, power supplies, ethernet filtering, cabling, switches, etc.

I eventually bought a used DCS Network Bridge and did a number of additional upgrades to power, filtering, and cables on the network front end. (FWIW, a straight swap-out of the DCS in place of the Sonos was a surprising revelation in improved SQ on its own.)

In my system, all these changes were an upgrade in SQ. Ben at Mojo Audio was right. There are of course diminishing returns in cost, but I have no regrets.

For you Deezer users out there, the SimAudio Moon Mind2, NAD M50.2, and DCS Network Bridge support native Deezer streaming. They are the only higher tier products I’ve found that support it.

@veroguy  great post  really quite helpful  thanks