SACD/CD Drive Mechanism Replacement

I do it all.  CDs, SACDs, Streaming.  Not big on vinyl but I do have an analog rig that I use for LPs no longer digitally available or where I prefer the lp mastering to the digital rendition.

  SACDs when done right can be breathtaking in their realism.  Since you don’t own any SACDs, my practical suggestion is that if you buy a player, new or used, it isn’t going to get a lot of wear and tear for a while.  If I was in your shoes I would buy the used Esoteric, because they are as good as it gets in SACD.  Don’t waste money on an extra drive that you may not be able to install due to the reasons that the OP has identified.  If it goes, decide at that time if SACD is something that you really need in your life.  If it is, there will still be manufacturers.  SACD is valued a lot more in the Far East than in the West so someone will be making them for at least the next quarter century 

If you are going to explore streaming, and are new to it, you might not want to spend a lot initially on an expensive streamer such as Aurender, because some people just don’t get into it.  Streamers are networking computers , gussied up to look like audio components.  They are subject to the the same foibles that networking computers have.  So for example if you have ever had a printer go offline on you, when you didn’t do a darn thing to cause it, and been driven mad until you resolved it, there may be some of that in streaming.  Frequently software updates by either the streaming service (Spotify, Qobuz, etc) or by the streamer manufacturer, or even your internet provider, may cause incompatibility issues, and the various companies will point fingers at each other and leave you in the lurch.  
  I mention these issues, OP, because you have stated you don’t feel comfortable with IT issues.  I’m not particularly IT fluent, but I’ve been streaming for years.  I generally have been able to navigate the frequent problems, but in one case I ultimately sold off an expensive streamer, a Bryston, because it was so buggy and because it’s software program was basically unusable.  If you love CDs, it’s really hard to beat plug and play.  And while there are endless debates here about which sounds better, equivalent price level CDPs and streamers sound about the same in quality.

  If you are using an external DAC, I would stream initially with your MacBook.  You can load the service on the computer and see how you like streaming.  If you love streaming I would still upgrade the CDP and then do it all.

They aren’t mutually exclusive technologies.  You can enjoy your CD collection and stream simultaneously