Comentário oficial
All that you mention (minus the CDJ-400) are supported; any player that previously supported rekordbox playback is capable, and the soundcard will be able to output the audio while the controls manipulate the playback.
To be honest, if you're using the more advanced CDJs (like a CDJ-2000 or CDJ-900nexus), the better way to use them is with the LINK as you will have the CDJs performing the hard work (audio processing) and then you'll also have waveforms in the displays.