Good question! I had to think about this a bit! My immediate thoughts when I seen this question off the top of my head were Neumann 120, Genelec 8330, Mackie 824 and maybe even a Kali IN-5/8 or JBL 308 I might choose over Kef R3.
Darn, then I realized I had to think passive speaker. Without being able to listen again and compare the Paradigm Founder 40 and Revel Performa3 M106 were the only ones I would probably choose over the R3 off the top of my head. After some thinking there are others I would consider but would definitely want to listen or listen again. Those would be Focal Aria 906, Elac DBR62 and Martin Logan XT-B100. Now what I would choose personally and what I recommend to customers is different and that is based off experience of doing this 25+ years.
Where I work we do not have a showroom so we don't do customer demos too often. We will demo speakers or let customers take speakers home to demo if it happens we have something in stock. That's why I recommend to customers to go to dealers with showrooms and listen to see what they prefer. I know some of these dealers will also let customers try speakers at home. I often recommend a number of brands/ models to listen in their price range but they are often not speakers I would personally choose. I will typically tell them to look at B&W, Sonus Faber, Revel, Paradigm, Elac, Monitor Audio, Focal, Kef and others and will tell them dealers relatively close (within a 100 miles) that have decent inventory to demo. In my experience most customers have chose speakers that I personally wouldn't, often ones that don't measure well. It could be aesthetics, it could be they have good sales persons, or whatever reason. That's why I think Harman's studies are missing some variables because this has happened almost everytime. This is why I recommend people try speakers first and don't go off measurements or reviews alone. YMMV.
Imho, the main problem is…
You think the harman study alone is what you have to learn, but its not..
In the end is kind of complicated understand the whole thing.
For example, the harman curve alone tell you something very important, you may have to like or dislike it. Because, the study also tell you 25% of the people will prefer a brighter sound and 25% of the people will prefer a smoother sound. (If I remember the % correctly).
Also measurements, tell you flaws of the speakers, a good example is the r3 by amir. The speaker got recommended even with the room mode problem just because measurements tell you is a great speakers,
that speaker was one of the early speakers review, in fact if you followed the whole review, members pointed to “add the small edit “ because he talk about that room mode in later pages/post.
I dont think measurements are missing anything, often people said that but never point what.
There harman curve is just a preference, just like narrow vs wide directivity. You have to choose.
Also demos in the store are worthless, is much better demos at home, because the user will hear his room in the end, with his problem, but the other problem if the guy has enough time to optimize the placement and correct the bass response.
For example a cancellation in the bass could lead to a brighter sound experience. At this day, i havent see any store with acoustic treatment, even in big ones.
Another problem is for example, the guy likes smooth speakers but the r3 as i showed is not a smooth speaker.
Edit: Also he pointed the volume thing, but there is something called fletcher curve, your ears listen different at different volume level. Some active speakers fix this problem but passive ones dont change his FR at volume variation.