You're right, did I write that. That 5-10 nS of difference in delay will kill the imaging of the deep bass much more than a class D amp with $15 worth of parts.
I know nothing of Def Tech products other than where they are sold. Speakers have a huge markup. How do they compare with ACI's lineup sold online only? Are they class D or maybe a "sunfire" amp? In any case the power supply of a decent amp is not very practical in a speaker and not that cheap. The amps themselves are pretty cheap with a good 400+ watt amp setting you back less than $200, parts cost. All that brings the cost up to a point most consumers won't spend on speakers. That's why class D is attractive. In all fairness the distortion at 80 Hz and below is pretty high on even the most expensive speakers and will swamp out any non-linearity from whatever amp is driving them, aside from tubes of course.
I was really pinging Slick1964 on his comment on delay and imaging. Deep bass is pretty much non-directional therefore imaging and soundstage are irrelevant as pointed out in a previous post. None of this is really helpful to the original post so I will go back to lurking.