A move from Harbeth to... Wilson?

"Anyone who thinks they are HiFi sounding has not listened to current models..."

I can't tell you how many times I've heard this about several brands of speakers over the years.  Basically, it boils down to "THIS TIME we got it right."  ;-)

I begrudge no one for whatever preferences they have. We all have different priorities concerning what we value when we listen to music. That's fine. It's a big world and there are options for everyone. 

(And, BTW, I do listen to live music regularly -- Powell Symphony Hall, Cathedral Basilica and similar venues these days and years ago spent time in the music industry as a sound engineer before switching careers. I'm confident of my own preferences.)

Great room size. Great Amp. You really have to listen to the Sabrinas.
The Harbeth you have would go nicely with two REL s/510.
The Sabrinas are very different then the Vintage watt /puppys.
Very transparent and open. If you listen to them you will decide quickly if they work with you.

Going from Harbeth to Wilson is an interesting direction.  I will admit my bias against Wilson speakers.  I have listened to many models over the last several years and the last ones were at RMAF in 2019.  I find them too clinical in the top end and also the integration of the midrange and bass just strikes me as unbalanced.  Perhaps if they are really set up well my opinion would change but I have heard them with top notch solid state and tube electronics.  My test is always violin music and the upper frequencies just drive me out of the room.  I settled on Vienna Acoustics Liszt when I was doing my search.  I guess everyone has different priorities that they value.  

I have had one experience with a Wilson speaker, so I am far from an expert, but I will give you my experience.   I would demo the speaker, preferably in your setup, but if not, then at a dealer.  I would not buy them without listening to them first.

This is my experience with the Wilson Watt Puppy.   The dealer was extremely nice and did a tour of the system the Watt Puppies were connected to, showed me how to adjust the Watch Dog subwoofer, pointed at a huge collection of CD's and said, "You can stay as long as you want, if you have questions, come and get me," and then left the demo room.

A friend and I spent the next two hours listening to the speakers and playing around with different adjustments on the Watch Dog.  There was a seat between the two speakers and if you were in that chair, there was the most three dimensional, accurate, pleasant sound I've ever experienced from a music system.  HOWEVER, if you moved left or right, changed seating height the sound stage became flat and no different than fifty other speakers I've heard.

The Watt Puppy speakers were extremely accurate, but also, extremely directional with a very, very small soundstage.  Whether that's the case with the Wilson speakers you're considering is unknown, but you should listen to them very carefully before buying them.

OP: check out the room size here:
https://www.whatsbestforum.com/threads/harbeth-monitor-40-2.25222/