What am I missing streaming music with a Node 2i

I haven’t really done much A/B between my DACs output with Tidal @96k compared to the Vault 2i analog out streaming MQA but both sound great.   I think in general my DAC sounds better but the Vault sounds pretty good given it’s modest price.   I don’t know if it’s in the remastering but some MQA titles sound better to me but some aren’t as good as their 44.1 counterparts.   

Another option to the Lumin D2 is the Teac Reference NT-505 though in addition to streaming like the Lumin it also has the ability to serve as a full function DAC.  I have owned both and prefer the AKM 4497's in the Teac over the Wolfson chipset in the Lumin.  Both use the Lumin app for a control app.  

The Teac NT-505 looks really appealing because of the ability to hook it up directly to the amp. There is also a lot of options for hooking up different digital sources, a NAS and flash drives + headphones. My tube amp uses RCA's and the Teac uses XLR connections. I'm going to ask a possibly stupid question, can I have them both hooked up to the amp at the same time and turn on the one I want, the tube pre will be relegated to phono duty only after I sell the Node 2i.

Not sure I understand what you're asking.  The Teac has both SE and Balanced analog outputs but I don't know if you can hook up both at the same time.  If you are using your Marantz as a control center including bass management how are you going to do those things.  Tell me exactly what you are proposing including the specific gear included.  I have mine connected via balanced IC's to my BHK preamp with the volume on the Teac at unity gain.

The Marantz SR 5012 is for surround sound with tv only. I have a Odyssey Stratos stereo amp and Odyssey Candela tube preamp for 2 channel listening. The Candela has a HT bypass so I can use the mains for the fronts in the surround setup. I am running the Node through the Candela as well. What I'm proposing is using the SE inputs for the Candela and the Balanced for the NT-505 on the same amp. It doesn't sound right to me but I don't want to run the NT-505 through the Candela.