If you want multiple channels of audio being recorded from the Ensoniq, then you will need an interface with more inputs than the AudioBox USB. If you are looking at 16 tracks then your best bet is a USB interface with at least 16 tracks or the ability to expand or daisy chain for more inputs.
For just MIDI data then yes you can record all 16 channels of MIDI data from the Ensoniq; just set up multiple instrument tracks and set each one to a particular MIDI channel that you want to record. However this is just MIDI data and no sound or information about what sound was being played will be preserved, just the notes an associated control messages.
You may wish to check out the Knowledge Base on the PreSonus website for further information regarding setting up MIDI routing and using external instruments.