Remarkably better sound possible with just 1 system component change?

I could have posted this discussion to a few other categories but chose this one because discussions related to 2 of the 4 components in question belong here.

So it's been ~2.5 yrs since I purchased my current system. I did a lot of research at the time here on audiogon, but no auditioning, and put together a system that sounds very, very good to me.

While I have no complaints, the itch to upgrade has surfaced recently.

I am curious as to whether you guys think it will be possible for me to replace just 1 of my primary 4 components and obtain significantly better sound as a result. The more discernible and obvious the sound improvement, the better obviously. I am not looking for a marginal upgrade - I want dramatically better sound. And I am not looking to replace more than 1 component at this time. I am hoping to get a few ideas/candidates and then may decide to audition some of the recommendations before making a decision. Hopefully some of the upgrade paths are such no-brainers that I may even be able to take a leap of faith without auditioning. Note also that acoustic room treatments are not viable in my current listening location.
My current 4 part system:

1. Lumin D2 - 100% of my listening is streaming via Tidal
2. Mcintosh C2600 preamp
3. Mcintosh MC452 amp
4. Focal Kanta 2 speakers

Cables are Cardas Golden presence RCAs from the Lumin to C2600, Cardas Clear Cygnus XLRs from the C2600 to the MC452, and Kimber 8TC speaker cables to the Kantas.

Soundstaging, dynamics, imaging and overall clarity are all great. I have to say I love the Be tweeters. And the bass is punchy, tight, fast and certainly sufficient for my needs. Vocals and overall sound are warm, liquid smooth and analog-like, just the way I like it. (Forgive me if I've botched some of the characterizations - I'm no expert at this). The only thing I can think of that could use some improvement is the sound quality at lower volume levels, although that is not terribly important to me since most of my listening is in the 90+ Db range. Would be nice, though.

So while I do love the overall sound, surely dramatically better sound can be obtained via a 1 component swap? Budget is ~10k. Or will I need to spend more, or upgrade more than 1 component to achieve the desired result?

Thanks in advance for your time and thoughts.

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Would just get the best Audioquest power conditioner you can afford.Will make every component perform better.
I'd call Vintage Tube Services and see if there are tubes that would elevate that MC 2600.  
You’ve obviously gotten a lot of suggestions, but I’ll add to the pile.

The two upgrades that made far more impact than I was expecting were adding power regeneration (in my case a PS Audio Power Plant 12) and Isoacoustics Gaia feet to decouple my speakers from the floor. Both were nearly as dramatic as any non-speaker upgrade I’ve done.

Agreed with the other person in the thread who said that given how sensitive your speakers are, a lower-powered tube amp might improve things quite a bit too.
You may want to consider adding instead of replacing.   and With the Be tweeter and with Focal's famous 6.5" mids, I'm sure the vocals are terrific as you mention. However, the Kanta 2 speakers only go down to 35Hz. Not surprising for a pair of 6.5" woofers. You say the bass is 'punchy'.  Punchy bass usually means bass you can hear, not feel.  A subwoofer may add what you're looking for by providing bass and slam that you can feel, especially at low listening levels.  And you'd only need to spend $2,000 - $3,000.