Según la web de Roland los dos modelos existentes son el td-9 k y el td-9 kx, y este es el cuadro de componentes y lo que literalmente ponen en su FAQ:
A.Though both the TD-9K-S and TD-9KX use the same TD-9 sound module and MDS-9 drum stand, there are differences in the pad configurations.
(See the chart below.)
One strong point is the 3-way triggering on the Ride cymbal with the TD-9KX, using the CY-12R/C. It is not with possible with the TD-9K as a CY-8 pad is used for the ride. (But you can add an optional CY-12R/C or CY-15)