What do you look for in damping factor?

Audiokinesis, high damping factors don't automatically indicate high global feedback.
So high damping factor does not necessarily imply sonic trade offs in other areas.
As you've posted in earlier threads, it's easier to make a speaker with a low impedance to have an ultra smooth impedance curve, so there are no impedance curve bumps to modulate the frequency response. Typically speakers with such a low impedance are driven with amplifiers with high damping factors.
Are you suggesting that your bumping the impedance in the bass region to correct for a fundamental flaw? Using a port will of course compromise phase and time accuracy.
Th impedance curve of the Maggie's will work well with high damping factor amps well.
I would suggest choosing a speaker that fits into ones budget, room accommodations, listening tastes, then choose the appropriate type(s) of amplification, and then make ones final amplifier choice.

Unsound, what Duke was alluding to is that speakers can be designed using either the Voltage Paradigm or the Power Paradigm.

In the case of one of the speakers he mentioned, he set the port resonance *below* the cutoff of the speaker. Now with a Voltage Paradigm amp, this would have been a roll-off in the bass. But with an amp with a higher output impedance (Power Paradigm), it instead extended the bass response another half octave- to 25Hz. I've heard him call this his 'free lunch'.

Atmasphere, thanks. That appears clever, but I still think the use of ports come with a price. So much for free lunch?

Unsound, for that you would have to hear them. I know one person that used such speakers to replace a set of Carver Silver Amazing loudspeakers- he likes Duke's speakers better because they are smaller, are easier to drive, sound better overall and of course go deeper in the bass.

Of course those are all good reasons to like a speaker, but, amongst other things, ports can compromise time and phase fidelity. Obviously, some feel the trade off worth it.