I have a Naniwa 12K, a Shapton Glass 16K and Suehiro G20K. I also have several natural finishers. The Naniwa was my first finishing hone. Although it is capable of producing a keen edge, I never was able to produce an edge that was both keen and smooth. The Naniwa 12K produces a harsh edge if you over-hone.
At least in my experience, the Suehiro 20K seems to be immune from over-honing. Yet it has enough abrasive capability to go all the way from bevel set to finishing if you have the patience to do so. This is exhibited in a couple of YouTube posted by a member of the SRP forum. This versatility makes the stone easy to use as a finisher.
If you are getting edges with your current honing/stropping methods that suit your preference based on your beard coarseness and skin sensitivity, then there is no need to spend the money on a G20K. I have never used the Dovo black stropping paste, but I have used CBN spray as fine as 0.1 micron, even after the G0K, which is advertised as about 0.5 micron.
With the wide variety of synthetic and natural hones and lapping films and the variety of polishing pastes and sprays and stropping substrates, there are numerous ways of achieving the results you desire while still staying within budget constraints.