Phil - thanks for asking the question, and I think the sarcasm is a bit misplaced when not only does the spec on the Autonomic website not give the polarity, but it also doesn't specify the physical connector size.
I've been in precisely the same situation as you, and found out the hard way (after buying a suitable PSU which had the wrong plug dimensions, and then multiple attempts at different connectors, none of which would seat correctly) that the DC power jack isn't that easy to match.? From the info that sound.scan posted, it looks like it's a 5.5mm OD 2.5mm pin, so I may have another go now - but I ended up getting an ATX 4 pin power connector and connecting it up to the board (the connector is just behind the jack when you lift the lid) and using that instead as it's just for use in the office (it's easy to see the correct?polarity that way too).
All the best,
Ol