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

Speakers make the biggest bang-for-the-buck! I will recommend a pair of the latest Quad ESL's. Your electronics gear is fine. The stock power cords are fine. The interconnects are fine. Others here will disagree with my views about cables/speaker wire. My experience goes back to 1976 when I bought my first really good HiFi system.

You didn't list your present phono cartridge. This being a mechanical transducer like a speaker will have a different sound compared to other companies' cartridges. And like speakers subjective impressions are important. You might want to buy and try a different phono cartridge.

After a certain point it's not about the equipment, but how you setup the equipment in your room.  You have very good equipment that would easily reveal the benefits of good setup.

First experiment with finding the optimal speaker/listening positions.  Here you're really looking for the smoothest bass response and most precise imaging/soundstage info.  Inches matter.

Second, are all your components positioned on solid, non resonant surfaces?  This is particularly important for your turntable.

Third, meticulously align your cartridge/tonearm.

At this point your basics are covered.  If you want to go further you could explore room acoustic treatments, cabling and power conditioning.  Careful setup is time consuming, but it's cheap.  The rest of the stuff can get very expensive.