Noob question about streaming . . .

Okay, I’m not exactly a Luddite, but my audio journey started in the 70’s with Marantz separates, JBL speakers and a Dual turntable. Thaw about thirty years ago I got into home theater, with Parasound separates and four Bose 901s (no haters please — they work well for watching movies). 

Anyway, my Parasound AV preamp died, and I replaced it with a Marantz AV7706 preamp. I’m starting to explore its capabilities, which are light years beyond the old Parasound unit. I’m also exploring using it for music listening in addition to home theater, but streaming is new to me.  (I’m also exploring new speakers, but that’s a discussion for another day). 
 

So, with that background, here are my questions. I’m using the HEOS in the Marantz to stream music through Spotify, which I’ve used in my car for several years. Would a separate streamer be a significant improvement over what I have now?  My understanding is the Marantz’ built in DAC is good enough that I don’t need a separate DAC, unless I’m going to spend big money on one, which I’m not inclined to do right now (speakers first). Second, would a streaming service like Roon or Qubuz or Tidal provide significantly better music quality?  Spotify provides access to all the music I want, but I do realize that it’s limited in terms of sound quality. Help educate this old dinosaur. Thanks!