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

I bought new Quad ESL's 15 years ago - and I'm keeping them. The 29 series is very smooth and elegant, and build quality is high. The 28 series is brighter, too bright for my taste. YMMV

What are your ears missing?  What do you want to hear more of.  What kind of music do you listen to?

Remarkably, no one's touched on the elephant in the room:  You've got all this McIntosh gear and are using a low-fi piece of junk ADC equalizer.  First thing I would do is ditch it.  You will find that the system suddenly sounds more open, with better dynamics, lower noise, and less graininess.

I’d agree with @jhnnrrs about the equalizer you have in the chain.  I’m not sure why you would need it given you have an 8 band in the preamp.  Pull that thing out and get yourself a nice external DAC.  Not sure how much of your listening is digital vice vinyl but an external DAC would likely make a huge difference depending on budget.  You could likely do better for speakers given the level of your other components but I’ve never heard the Spendors.

- Get a Rythmik F12G subwoofer or a pair and cure the Spendor’s flaccidity.

- Get rid of the Panamax and get a Audioquest Powerquest 505, 707 (if on a budget) or something from the Niagara series and plug all your stuff into it. You should be able to perceive more resolution, detail, etc with the latter.

- The room is atleast 50%. Figure out how to treat your room, if you haven’t done so already. If you don’t know much about it, talk to a guy like Matthew Poes (Poes Acoustics). The 150 bucks or so that a knowledgeable acoustics guy may charge for a phone consultation should help you not make mistakes/waste cash and get you far.