It's the Focal speakers! You don't like the treble sound. Changing electronics/wire will not alter this! Time to sell the Focal's and get  different speakers.

My nephew owns those Focals and loves the sound. Many  find Focals very detailed and bright sounding. Since you have subwoofers I doubt you would go wrong with a British stand mount speaker. Spendor, Harbeth, Graham, Falcon, etc.

Are Focal Speakers Bright-Sounding?

Focal speakers are often described as bright or bold, but whether they sound “too bright” depends on your listening preferences, system setup, and how they’re installed.

Why they’re perceived as bright
Focal’s design prioritizes clarity, detail, and extended treble. Their inverted-dome tweeters and advanced cone materials are engineered to reveal subtle musical information, which can make vocals and instruments “pop” Focal Australia. This high-fidelity, forward-hi-fi sound is a hallmark of the brand, and in many listeners’ ears, it translates to a bright, dynamic, and energetic presentation smart.dhgate.com.

When the brightness is noticeable
Some people find Focal’s treble aggressive or fatiguing at higher volumes or in poorly tuned systems. Common causes include:

• Factory head units with limited DSP that exaggerate upper mids and treble.

• Incorrect crossover or gain settings that push tweeters forward.

• Tweeter placement or aiming that directs high frequencies directly into your ears.

• Weak midbass support, making the treble feel more prominent.

• Personal preference for a warmer, more rolled-off sound Focal Australia.

How they’re actually voiced
In a well-designed, properly tuned system, Focal’s sound is neutral rather than artificially soft or dark. The treble is extended and precise, the midrange is natural, and the bass is controlled Focal Australia. This balance gives a spacious soundstage and long-term listening comfort, but the clarity and detail can feel “bright” to those used to smoother, more bass-heavy systems.

Bottom line
Focal speakers are not inherently harsh—they’re designed to be detailed and revealing. If you like a bold, energetic, and transparent sound, they can be a great match. If you prefer a warmer, more laid-back tone, you may need to adjust your system setup or source equipment to tame the treble.

Ditto!  

Given you have addressed acoustic issues with your room, the only logical thing is going to a different speaker.  That is the elephant in your music room!

I am always amused how some will do anything BUT replacing a bright speaker.  New DAC's, cables, tubes are not going to change this to a significant degree. System building always starts with a speaker you love.  And I mean 100% love.  Then pick the gears that will further complement the qualities you are looking for in your system.  If you you are making roast beef, seasoning is not going to turn it into roast pork!  Start with what really makes you happy--with no reservations.

Adding felt tweeter rings are easy to try.  Or you can experiment by treating various places along the speaker baffle.  Simple, cheap, adjustable, reversible.  Spica and Vandersteen have used that approach.

I’m guessing room acoustics, too. I pretty sure that’s what keeps my stuff from sounding better.