Hi Minor
I know you posted a while ago, but did you get the microbrute? It is great fun, I really recommend it.
I assume with the sub phatty that you can set key priority to high, low, or last. I tested on my Sub 37, set that to low note priority, set the microbrute to high note using the Microbrute Control Centre software, and connected the two via DIN MIDI cable.
It works!
If you hold a single note, it will play on both, but play two notes, and the low notes play on the Sub, and the high on the Brute.
Hope that helps