Upgrade my HiFi setup!

You can add the KEF KC62 sub to the mix and get the LS50 Meta. That is a surprisingly great sound in a small-ish space. 

I replaced the LS50 Meta + KC62 sub with the Magnepan LRS+ and then the  Magnepan Mini. I went to smaller office spaces. The Magnepan Mini is using the same panel as the 3,7 but much smaller.

I think the following would be great:

• Magnepan 3.7 speakers (used)
• Schitt Audio Wotan amp ($2k)
• Benchmark LA4 preamp ($2.5k or less used)
• Schitt Byggi DAC ($3.5k) (has a digital volume control as an option)
• Benchmark XLR & RCA interconnects (low cost and great for Benchmark and Schitt)

My office setup is the same except I have the Mini speakers. This thing sounds so good. Do not be fooled by the low cost of the Wotan amp, it is superb, but it needs a lot of play to settle into my current sound. I do not have the Schitt Byggi DAC yet, I am in the queue to get it in the next few weeks. I have the Schitt Yggi+ OG on my office system and if they still sold it I would easily reconned it over the unheard Byggi. Though rumors are that the Byggi is the best DAC they ever made.

BTW - I recently heard a preamp that I liked better than the LA4. That was a tube preamp which was as detailed as the LA4 but with tubes. It cost $33k.

I also heard a tube DAC that I liked better than the Yggi+ OG DAC, but that DAC cost $24k. Only 2 items I would consider changing the LA4 or Yggi+ OG DACs for. Luckily, I cannot afford them.

Well I would go big or go home...stop messing around.....get 300B amp and a pair of speaker like the Devore O/baby Speakers.....please don't tell me they don't have the bass you "feel you need" ...forget room size what matters is your sitting position in relation to the speakers...you don't need a PA system to fill the room that is all BS...If you have a DAC with a volume control and you are not listening to vinyl that that will work...start there. You can easily rival the "big time-expensive systems " start with the music that moves your soul.

With respect to your speakers only, if you are happy with the stand mount set up, I would consider a pair of Dynaudio Contour 20i's or better yet the confidence 20's. 
They are better.  The big advantage of the Confidence 20's, besides the better tweeters, is the down firing ports that allow closer placement to the rear wall.  I replaced very large Revel Salon 2's with the Confidence 20's and they are better in all ways.  Their ability to scale in a large room is phenomenal.  I  do use a pair of REL Carbon Specials. but even turned off the Dynaudio's are impressive.  Resale value remains good as well. Note however that they crave power and current, and reward good electronics.

Is the 7 Years experience solely of the Kef and Rega, or have you ventured out to take on board what other arrangements of Audio Equipment can produce as an End Sound??

Mentioning $10K on the Gon is going to attract various attention and intentions for such a budget, which can expose an individual to being steered in directions that may be not the most advantageous to your new direction being planned.

Do not buy on forum recommendations, take info offered as a means to a further investigations and gather useful info.

Create a Shortlist and invest some of the $10K budget in creating a opportunity to listen to End Sound being produced by shortlist devices and others that may present themselves.

Act in Haste - Repent at Leisure

Caveat Emptor is ones best friend when going on this journey type.

Do not overlook the Kit Market, which is the 'Road Less Travelled',  where an option is to have a device purchased which can be commission built on ones behalf.

Most of my equipment comes from this method of purchase and it is not uncommon if approached with a reasonable understanding to acquire audio devices that will requires  4-5x the spend to achieve an End Sound from the commercial world that can start to compete in this area.  

A Neurochrome Power Amplifier, I have a module 65 in my home at the current time along with a few Speakers that are Commission Built from a Kit Design.

 https://forum.audiogon.com/discussions/diy-speaker-kits-a-good-idea

Using the suggested purchase methodology and having an audio device built, at a price of $2.5K - $5K can easily get a system in place that can create need for a Budget to extend to near $15K - $20K to better it, if off the shelf commercial items are being selected that can compete with the End Sound being produced, maybe even at used item prices.

Purchasing KIT/DIY or products with little or no brand recognition can offer a high level of performance/price ratio but with caveats. Resale value is non-existent, customer service/repairs are an issue, company longevity is at a greater risk. Purchasing this type of gear does not make you "smarter than the next guy" or I’m sticking it to the big guy, why would you desire that type of attitude? The 4x-5x greater price/performance ratio is grossly overstated. I have heard many kit and off brand speakers, at best there competitive with the mainstream competition.