if you had this system, what would you do to make it sound the best you can

I’d start by watching videos on speaker placement  and room treatment. That’s free, and often can make a huge difference.

Second, instead of casting about wildly, test your system and see what is going on.

There is free room acoustic software called  “REW”.  For whatever reason I can’t post a link due to how they set this website up.  But you can run it with a computer, DAC, and a cheap (like $20) omnidirectional microphone.  It will test your system and room acoustics and tell you what is going on.  Very easy to use.  Starting with this software, I literally made a Cold War era bomb shelter into a ln amazing listening space.

Third, Google lists of songs reviewers use to test equipment and what they are used for.  Resolution, bass, separation, etc.  it’s things like “can you hear John’s squeaky chair at the end of a particular Sgt Pepper song?  can you close your eyes and tell the five singers in Y are placed.  Does a Queen song song right?  Does Lourde’s bass in “royals” pound your chest? This is actually fun. And was a fair amount of music I never listen to.

Do all that, and you’ll find your weak link.  If I am guessing, I bet it will be your speakers, which are actually great speakers for their price, but not as nice as your amp, for example.  That said, it may be as simple as buying a subwoofer and adding to those speakers and setting it up with a high pass filter so your main speakers don't have to work so hard.  Perhaps a split before the amp, even.  Just depends on what you buy.

Second guess is the amp, third would be your cartridge.  And that could be how it is installed, which you can also check for free.

What the problem IS NOT are interconnections. That’s an issue for extremely high fidelity systems.  So unless you are using lamp wire,‘don’t concern yourself with that now. Utter waste of money with this system.

it is not your main wires, either.  Farther down the list than interconnects.  It could be (if you hear buzzing or pops or whatever) bad electricity coming in.  A reasonable Furman power conditioner might help and is good insurance from power surges.  This depends on your house and your local power.  But is majoring in minors, typically.

If it were my system, add a stereo pair of subs. Something small and fast like REL T7/x or T9/x depending on size of room. Spend the time learning about positioning and dialing them in properly.

Yes on all of the above. McIntosh is very warm sounding. Silver interconnects from your source to your McIntosh. I agree, ditch the equalizer... more wires to contend with. 

Upgrading the fuse. Makes a difference! Yes on a power conditioner. A used Niagara will lower the sound floor. Sort of the difference between driving in your car with the stereo on versus, sitting in your driveway with the music on. 

If you keep the speakers, a sub will make a huge difference. 

It's unfortunate, but Everything makes a difference. Only your ears can make you a believer. 

My system, Lumin T2 streamer,-- AQ Wel xlr --McIntosh MA 12000 with purple fuse--AQ Firebird speaker wires--GR Research NX-Oticas speakers with two Double trouble subs. 

I also just added a McIntosh MEN220, room correction unit. That unit made a big difference and balanced not only the room, but also the phase and the frequencies between my speakers and the subs. Impressive difference.  

Panamax power conditioner should go. I have one and don’t use it in my System, it tends to be restrictive.

What is size of room which really impacts Quality of what you're hearing.  I would for more powerful amplifiers, mcIntosh is fine

I suggest taking some of your upgrade budget and attend an audio show. AXPONA is coming up but there are shows all over the country now. There is no better way to get an idea of how your system stacks up against what is currently available.

I could easily post the same question you have but I don't need to. I'm running a late '90's vintage system with Krell amp and preamp and Thiel CS6 speakers. When they were new they were solid Class A. I've been to three audio shows (AXPONA, Florida, PNW) and I found out that my system holds its own against most of the six-figure systems I heard. In many cases my setup sounds clearly superior to systems where the cabling and power conditioning cost more than my entire rig.

You will hear lots of speakers and some of them will tickle your fancy (I think the rest of your system is fine). You will see that high end speakers sound REALLY different from each other and what you like may be the opposite of what someone else likes. At the 2018 AXPONA they had a pair of large Wilson speakers in a well appointed room and I thought they sounded like fingernails on a chalkboard. Other people I talked to thought they were the best sound at the show. Once you go through this process you can narrow down the choices and make an informed decision. And besides, it's just plain fun.