Yes, it might be a good idea to stop buying stones for me too.
I'm not talking about sharper than 6k. Sharper than the 99% of the European stones I have used, and I have some experience with many of them.
I have a combo sigma select 6k/13k.
The 13k performs the same with the shapton 16k. Those edges are extremely sharp, but not smooth, and I can't appreciate their sharpness this way. I like my edges super smooth, I don't enjoy shaving with most of the extremely fine man made stones.
Used with slurry, the Shobu gives an edge as sharp but very smooth. If used with plain water, or something like Smith's solution, I'm sure it can give even sharper edges than those stones, but again, I'm guessing that they won't be as smooth.