DAC upgrade or Amplifier


Which has more influence over the soundstage - the DAC or the amp? My sound stage is high and wide, but recordings sound 3 dimensional only rarely. My equipment is at best mid fi - Adcom 5500 amp and Cambridge audio DAC magic. Listening primarily to Tidal at their highest level available.  The rest of the system if Adcom Preamp 750 (the Nelson Pass design), Tyler Acoustic speakers, tributary cables throughout. Any advice or suggestions for upgrades for improving the "depth" of the soundstage is appreciated (let's say that an upgrade for less than $1500 is in the budget, and I'm comfortable buying used from reputable sources). Thanks!

philtangerine
A Tube amp!  Adcom is pretty benign gear, they add very little coloration to the music.  I would start with amp (s) then look at devices.  I use to own a Adcom 750 GFP pre-amp along with the GFA 555 amps.  The soundstage was very wide but it missed the depth and instrument separation. 
Does the DAC Magic have the ability to unfold MQA files from Tidal? I have found that my Bluesound Node 2 is able to give me the best hi-res sound via MQA albums, not ALL MQA albums, just ones well recorded.
Another thing, I have tried bypassing my preamp and connecting my DAC/steamer directly to the amp. I would research this to see if your DAC Magic is capable of being used this way. I was very surprised that my preamp was not allowing the clarity and soundstage to come through the DAC to the amp.

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.
Thank you all who've commented so far. I'll start by pushing the TV back farther toward the wall to be sure the screen is at least 18 inches or more behind the speakers, and the speakers stay out at least 3 feet from the rear wall. @2psyop , Kalali's comments are correct. Even without the ability to unfold, MQA sounds to my ears like an upgrade vs standard CD, though I've read that you can't get the full benefit w/o an appropriate DAC.  I have gone direct to amp as you've suggested, but prefer the sound with the pre in the loop. @Auxinput, thank you for your thoughtful response. @vegasears can you suggest a tube amp (for under$1500)? 
Phil, I have not kept up with the latest and greatest in tube gear but I've alway liked Jolida products.