DAC upgrade or Amplifier

I have a DACmagic Plus and I know it does not support MQA. So in the OP's case, regardless of the streaming source, the output is not MQA'd (new verb).  I also did get an upgraded PS but a different brand from the one mentioned above. It did improve the SQ. In as far as soundstage depth is concerned, all things being equal, I've found the depth is directly proportional to the distance of the speakers from the back wall and how open is the area between them.

I assume by your reference to Nelson Pass you have a GFP-750 (as opposed to a GTP-750) and that's a pretty decent preamp. I have had the same unit paired with a GFA-555 for over 20 years now in my upstairs system but I only use it with a turntable. Its a really good preamp with a great deal of resolution and detail but not a great soundstage. I realized it when I put a tube preamp that I bought a month or so ago for another system in front of the Adcom amp and all of a sudden the soundstage depth became apparent. It also gave the tone a lot more texture and layers. The only obvious tradeoff was a bit of the detail and some bass was lost but the overall size of the stage was more tangible. I guess all I'm saying is start with cheap solutions first but ultimately you may want to consider a tube preamp since for me it had the most contribution to the overall sense of being there, while all other things being kept equal. By the way, my budget was a lot more limited than your - ~$800, so I'm sure you can do much better. All the best.