Music streamer with no DAC and no storage?

If you are looking for something simple to set up and use with USB output then the three top choices divided into two price categories for each company would be the Auralic Aries G1 or G2. the Lumin U1 Mini or U1 and the Innuous Zen Mk III or Zenith Mk III.  For each company the first choice is in the $2200 range and the second in the $4500 range.  Each is a reputable company with solid software and support. With the rest of your gear avoid these cheaper options unless streaming is just an afterthought.  

I have tried unsuccessfully with "just" streamers, Not only sound quality varies a lot but ease of use with the app. I have ended up, and I am currently happy with my Bryston bdp2 ( I have 2 of them!) and DCS upsampler (streamer included)
DCS do just a streamer (Network Bridge), which is one below the upsampler which is very good. In my view the only Naim product to compare is the top of range £10k + version (not the lower ones) but I don't think that gives such "value".
The bdp2 prices will have dropped to make it an absolute steal 2nd hand as the bdp3 is out and not a sonic improvement apparently.
I looked at the Bluesound and have been put off for reasons which escape me at the moment. From memory it was quality of sound and connectivity in my particular system.

Whilst writing I pondered over the use of Airplay suggested above, Airplay in Roon is far inferior  to normal wired ethernet so maybe the context I am missing on other products.

What do you intend to use as your music source and/or control app? That may play into recommendations. Most network streaming hardware does not include storage, and there are a fair number that don't include analog outputs, although I would say most of the less expensive ones do since most people would prefer to get more features than less.

I upgraded from the Node 2 to the Auralic G1 and couldn't be happier. It was a significant audio improvement but also added useful features like IR remote connectivity and an LCD screen to display album art via Roon.

I use digital coax to connect it to my Brooklyn DAC+. Coax sounded better than USB, not sure if it's attributed to the G1 or Brooklyn. 

Lastly, I researched the Lumin U1 Mini as well but there is so little info on it. It's $2k while the G1 is a couple hundred dollars more. Something to consider.