In response to http://www.audioroundtable.com/PiSpeakers/messages/1116.htmlNelson Pass has replied to me and said that the SoZ has an output impedance of "about 16 ohms".
So I'm not sure what that means in terms of damping factor or it's ability to drive 15" size woofers (low zmax?) at high SPL ?
If you're there Wayne - is 16 ohms pretty high?