The BK-9's MIDI implementation is quite advanced, allowing up to eight separate MIDI setups (combinations of channel selection for RH and Style/SMF Parts to be sent out via MIDI) freely linkable to each Performance.

So, essentially, you can pick and choose what gets sent to the SD-1 and what gets played by the BK-9, for each Performance.

And Tony... really? The best you can come up with is a suggestion to buy an as yet unreleased arranger that will be more than twice the OP's gear's cost combined? Right...