HEOS is a valid argument for the Marantz if you are committed to that.
Otherwise, the Sony will cover the CD player and streaming! If you buy in the $150 price range, it should also get you playback of SACD's (but verify that for the model you look at).
The long term durability of Marantz disc players has generally not been as good as the Sonys (even though the Sonys cost much less). I have a Sony CD player from the early 80's which still works fine! It is their bread and butter while Disc players are an "accessory" for Marantz.
The main thing is we have learned that the difference between a high dollar CD player and a low dollar DVD player is minimal when it comes to actually hearing a difference. You might be excited about that really cool looking new CD player and be convinced it sounds better (that is very human),but if you were blind to which was which, you would be hard pressed to hear a difference and without having some over- the-top speakers or using high quality headphones, I would not expect there to ba an audible difference.
It sounds like you are looking at an expensive BD player when the time comes and I say save your money. If you want better sound quality look at changes to your room, speakers, and/or subwoofer. Those are the places where you will make a decisive difference.
This is one of the most relevant points we can make to help people best spend their money - don't overbuy on electronics! Instead do research and make sure you have "good enough" electronics to power your speakers, ut then spend the extra money on the things that make a difference. Many of us here have spent big bucks on high dollar amplifiers. We fall prey to the excitement and convince ourselves that the new gear is a huge improvement, but after the "honeymoon" is over we pull out the old AVR and hook it up and realize it sounds as good as the high dollar amp (I am assuming the AVR was capable of driving the speakers properly).
I am a fan of your Klipsch speakers! I think they represent great value for their price. One thing you should know is if you decide to switch speakers, you may well need more than the 60WPC of the Onkyo! So if you ever change speakers (aside from switching to other Klipsch - which are efficient) you should also consider whether you would need another AVR/amp.
Simply put, if I see someone buying a Marantz CD player/streamer/amp, I see more money being spent than should.. An inexpensive Sony covers the bases shy of the Amp section (that you don't need). Also, for streaming, an Amazon fire stick or Roku provides a much nicer system for not much money and I have always gotten a real world improvement by changing my Roku every 2-3 years (snappy operation and streaming resolution more than sound quality). I consider a TV or BD Player more of a long term purchase and will keep a TV for over 10 years and a BD player for over 6. I definitely would not want to be using that 6 year old streaming device and it seems a waste to replace it because the streaming device is getting old enough to frustrate.
Could you get a Roku or Firestick and pull your DVD player from the HT room and buy a new HT BD player?
Understand, I have two Marantz AVR's and really like them, but AVR's are what Marantz does best.
For me. If you want a CD player - go Sony DVD
If you want an AVR, go Marantz, Denon, Yamaha, Onkyo, Pioneer, (or maybe Sony - they are still proving themselves as a low end AVR company)
If you want a streamer, go Roku or Amazon
Combining them all into one is only a good idea if you are looking for a compact system to fit on a shelf or something!
I think I have adequately explained why you are getting the feedback you are.
We will do our best to answer your specific questions, but it is hard to look away when we see "low hanging fruit" like you subwoofer which is a clear step down in quality for your speakers! Buy the other stuff if you like, but replacing that subwoofer is the biggest thing that will improve your sound. Most Klipsh subwoofers are not well designed, but they do have a quality sub in their R-112SW (avoid the R12SW!)
https://www.crutchfield.com/S-6onixHHSGke/p_714R112SW/Klipsch-Reference-R-112SW.html?XVINQ=GLX&awkw=683188894075&awat=pla&awnw=g&awcr=343141479351&awdv=c&awug=9010826&gclid=Cj0KCQjwoKzsBRC5ARIsAITcwXEXjZq8GEebrDd_eSLk8O0TilYj9LZiP3vp5iE_JtkM5ORfi3OjXKgaArOiEALw_wcB