"Is this the route you would recommend with the Nubatama? I know you were referring to another 1k stone, but if these take another "companion stone" to really shine, that could put these out of the running."
I am using the Nubatama Ume speckled 1k XX-hard, which is not sold on CKTG, I ordered it from Ken Schwartz. This particular stone feels coarser than 1k, say ~800 to me. I remember reading Jason B saying this was less true of the the medium hardness stone sold here on Mark's site, this one: http://www.chefknivestogo.com/nubatamaume1k1.html
As I said in an earlier post, I aim for a 2x-3x progression. So before I was using a 1k Ume speckled, 6k Arashiyama progression, a 6x jump. Adding the Nubatama 2k speckled gave me a 1k, 2k, 6k progression so that the first increment was 2x jump and the second increment was 3x. Adding one stone bridged a lot of real estate for me.
I also recommended above that you consider something like a 1k, Suehiro Rika combo and hold off on the coarse and finer stones for now. I think, though I do not personal experience with the Rika, that the Rika could segue with the 1k Ume speckled since it is generally considered closer to a ~3k stone.
My recommendation is to e-mail or phone Ken, he is the importer for the Nubatama line and has vastly more experience with all these stones than I do. Here is his contact info: contacting-me-t3134.html
. He is extremely helpful and would be able to tell you if, in his opinion, the Suehiro Rika and Nubatama 1k Ume speckled would play nicely together.