Yea, I did some further researching directly after I posted this message... and yep, I figured out the Outputs. The presets it came with from the previous owner were a mess, which led me to a knee-jerk reaction, of this machine is f'ked... but I replaced these with the Factory presets and low and behold, all now are playing fine. All 6 voices seem to be functioning correctly. So I'm happy.
I'm also happy that Midiquest seems to be integrating well so far - better than with my Korg MS2000. I created a fresh bank of awesome randomness last night, which gave me an insight into the Matrix's potential.