The dual-concentric KEF I auditioned was not the LS50, but did incorporate the same driver and employed a similar non-resonant cabinet design. To my ears, I felt the design goal was for a mid- to large-field image. Bear in mind that was one 30 minute audition in a dealer showroom with source material I did not know well. My belief is that KEF has paired a lower material cost approach with a great deal more engineering skull sweat. Whether or not my supposition is on the mark, the sound was not presented in a way that paid homage to the broadcast monitors deployed in cramped quarters of yore. I'm not at all certain how the speaker would fare in a desktop environment.
The traditional LS3/5A design pairs an extremely well-researched sealed volume and resonant cabinet with similarly proven drivers. The mid-bass bump @wrm57 mentions has been documented many times and is there for a reason: The design was intended to be used in a very small space (e.g. the interior of a broadcast van) with the engineer sitting perhaps three feet away with a noisy exterior environment. Clarity and definition across the transmissible dynamic and frequency ranges were the first priority with image created more by speaker placement than anything else. That bump allowed the engineer to hear things that could easily have been muffled or obscured by a passing truck or a cheering audience. That's also why there are entire volumes of commentary about "proper" LS3/5A height, distance from back / sides, toe-in, down / up angle and so on.
All of those things can make a difference to the listening experience with either design approach. The guidance you're really asking for is which one the AgoN forum participants feel would be better in your environment. If it was my money, I would definitely go with an LS3/5A variant because what you're doing is exactly what it was designed for from the moment the pencil first hit paper. It remains good enough to this day that it is a standard against which many other small speakers and certainly most source material, transcription decks and upstream electronics can be compared.
Your budget allows you to consider pretty much all of the best speakers the size class. As would most others here, I strongly suggest you go do a few auditions and attempt to mimic the distance and sitting height in your office area. My opinion is my opinion and may not be suitable for you. In full disclosure, I've owned a pair of the LS3/5A's big brother for decades (BBC LS3/6 / Rogers Studio 1 / Graham Audio LS8/1). I bought them back in the day when I was in the biz and had Accustat, B&W and DCM to compare them against on the shop floor. I have never tired of them and would be very hard-pressed to find something that sounds as good for 5 times what I paid in today's dollars. I turn the system on, stream some stuff to warm everything up then settle in. Then I start to tap my toes and smile. That's happy listening!