I'm not exactly sure yet how to route the audio since there are not many options, still have to hook it up to a setup & give it a shot. If any of you have a few ideas about this, feel free to drop it :)

I'm using the Rekordbox autogain-function (implemented in each deck) - Tempo is adjustable with the channel faders. RekordBox MIDI doesn't allow rotary-buttons to the gain or tempo. Maybe this will be an option in the future where there will be more MIDI-options at disposal.