Amp preamp impedance matching...can anyone explain?

Onhwy61, I think(?) I remember Jeff Rowland espousing such a philosophy. I also seem to remember(?:-)) past Audiogon contributor Sean suggesting the same thing. Some years ago Dave Wilson writing in The Absolute Sound offered a tiered approach to impedance matching.

Even with an ideal pre-amp to amp impedance match the B&K ST 140's sonic signature (as is the c-j's too) is a bit soft in deep bass, compounding it with a less than perfect impedance match might not be the best choice. I wouldn't recommend a low impedance speaker (<4 Ohms) with the B&K ST 140 either. Which is not to say that in an appropriate system the B&K ST 140 is not a good amp, as it certainly is, especially for the money. Keep in mind that the B&K ST 140 is getting a bit long in tooth and B&K is no longer in business. Though I would imagine that having the B&K ST 140 serviced by an outside source wouldn't be too difficult should the need arise.