Is there such a thing as a good medium priced music streamer?

Personally I don't feel $2 to $3k is medium priced. In between that price range, considering new and used you could try out some streamers from company's with a proven track record of making better than average sounding streamers...Innous, Aurender,  to name a couple. The rest of your system (quality, resolution) should play a role into how much you should spend as well. 

Do you need a streamer with a built in Dac? Or just a streaming transport (no dac)Or do you already own a Dac/Amp/Speakers worthy of a $3k streamer? Built in Dac or not should be your first hurdle or question to ask yourself. 

Lots of streamers out there to choose from..many different prices. I've tried a bunch of the more budget one's looking for that best SQ for cheap. Never tried the Eversolo's or Pro-jects but i have tried the rest of the usual suspects. The Wiim's, Node's, Cambridge CXN2 and their newest AXN model. Tried the Ifi, Arcam, B&W, and Pi. Some of those I kept for a little while, some not long at all. Most of these more budget models sound mostly the same (some will argue all transports sound the same), so the software becomes important. Currently I use a Primare Prisma, it's a transport only and sounds good to me. I use Chromecast to connect from most my music apps and for whatever reason Chromecast sounds great thru the Primare. The Halo Red is another streaming transport that gets good user reviews but I haven't heard that one either. 

If you want to step up your game the Innous models and their software seem like a real winner. I've heard one of their higher models and it was good..but so was the rest of the system. You could start of with something much cheaper with a return window and see how that works for you. A WiiM Pro Plus might be all you will ever need. I've experienced streaming thru Heos on a Denon product. The WiiM is a step up in my opinion. That new Eversolo 8 has a lot of capabilities if you need all that. Can speak for their software though. 

Yes I have a cocktail audio x45 it is 2800 new and it dose so much.it streams it plays and rips cd's it has a full digital recording unit in it it has a analog input and output allowing you to hook it in the tape loop of your preamp. It has 4 USB inputs a coax input a toslink input even a mm phono stage and can be used as a preamp if you want. I dont. Go to cocktail audio .com and check them out if interested .I really like the piece. Michael.

I ran a Zen Stream with an external linear power supply for maybe a couple of years. I really enjoyed it, There is room for improvement in the app. On 12/04/23 my new Volumio Rivo showed up. I was told it needed 200 hours burn in by the seller. I got a black friday deal with the linear power supply. Right out of the box, I wasn’t happy. Sound was bass heavy with a loss of highs. On day 4 I did an A-B using RCA SPDIF, and AES/EBU. The Zen Stream had a haze to it, the Rivo was very smooth, open, with a well defined bass with weight that I found convincing. I now have approx 225 hours on the unit. I run the unit output AES/EBU to a Gustard R26, into a Luxman L-550AXll, feeding Dynaudio Contour S 1.4. Delighted. It seems like I had more songs displayed (Tidal in Rivo app) on the Zen app that I do on the Rivo app.Perhaps not acclimated with app yet. Internet radio is awesome.

I can recommend the Bluesound Node or the Sonos Port. Sonos has the best app interface. Both of these devices will require an app interface. I can’t tell whether the use of the HEOS App is the source of your frustration with the Marantz ND8006 or if it is something else.  I have one in my living room now for 5 years, it is used only as a streamer anymore as I rarely use the transport and I use the DACs on my preamp. I get some of the complaint about the Marantz, for a time it kept requiring me to sign in with a password which for a non-keyboard device got old very fast. If I were replacing it today, I would buy a standalone streamer and separate transport and run each separately to the preamp. You could relieve the Marantz for transport duty only and get a streamer and DAC as separates if you don’t mind the extra power cabling.

Biggest problem for me with some of the higher end streamers is the limited support for streaming services; many don't support Amazon,  and very few support Idagio,  which are the two that I use the most, along with Internet Radio.  Innuos support says they are working towards support for both services,  but don’t know when they'll get there.  So I'm using a Bluesound Node as it supports a very wide range of streaming services,  including the two I use.  I  upgraded it with a linear power supply and the sq improved significantly.  I  use the coaxial out into my PS Audio Directstream DAC.  I  have a pretty resolving system,  and I think the results are really good.  And the new BlueOS operating system is very intuitive. Some think it's crazy to spend almost as much on the lps upgrade as the unit itself,  but the improvement was really worth it,  imo!! BTW,  I  am beta testing the upcoming PS Audio Stellar Gold Preamp,  and it is a fantastic unit. I  think it's as good or better than the BHK Signature Preamp at two thirds the cost.