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To use it with rekordbox dj (performance mode), no problem - connect both via USB and they're both acting as MIDI controllers for the software. Go into the MIDI manager in rekordbox, choose the drop-down at the left to select the KONTROL X1 and then map out whatever function you'd desire.
If you wanted to connect the X1 directly to the RX for stand-alone mode, no - sorry, that's not supported.