Official comment
You could theoretically create a multiple-device output using ASIO4ALL, then using that ASIO4ALL device in rekordbox, send the signal to both the SB and the SOLO, but you could also simply assign the SOLO as your computer's main output, then with the SB assigned as the audio device within rekordbox, engage the PC MASTER OUTPUT which duplicates the audio signal to whichever audio device is your main audio output for Windows.