interpretation of dealer speaker statement needed

Please tell me what this means in English; in advertising a pair of speakers for sale, the dealer said:

 "This speaker does have a combination of somewhat difficult impedance and negative phase angle in the upper bass, just like most loudspeakers of this type and size.  These are not a good match for SET-class amplifiers."

These are not oddball speakers but a very respected manufacturer.  They are a 3 way bass reflex,
 with (2) 6" woofers, a 6" mid-range, and a 1.1" silk dome tweeter. 

What is the dealer trying to convey?
 I read the statement as saying, they are finicky with the driving amp, and generally a high current solid state amp is recommended ( with the possibility of larger wattage tube amps ). Enjoy ! MrD.
And a SET amp in particular should be avoided!!!!
a pretty responsible dealer IMO

gbryant + 1. tomic, + 1, absolutely, as the dealer wants a happy customer, and would like to avoid a return of the speakers.
This is not unlike what you'd read in a Stereophile review, classifying speakers according tho how easy or difficult they are to drive.

In fact, chances are he/she copied it right out of a Stereophile review. :)