I agree what what labor says about the Cerax 320, I love the stone, but it is not from the traditional line. Sadly, I have not used the Chemical 320, which is from the traditional line so I will be of no use there. The Akamon 1k is very reminiscent of a king 1k, maybe even a bit softer but faster. The Kouga (3k) is slightly harder than the Rika (5k) and slightly less muddy. It leaves a very similar edge and finish, though. It still feels quite creamy feedback wise. The Shiramine (6k) is more similar to the kouga than the Rika as it, while a medium soft stone, is still slightly harder and less muddy than the Rika. It leaves a finer edge but a similar cosmetic finish. I W8 leaves a matte finish that has fair contrast and reminds me of a Gesshin 8k.
The cerax 320 and rika 5000 are the standouts, though, imo.