Matching preamp to amp

I posted this some time ago, but, I can't find it in the archives. It was originaly pubished in "the absolute sound" and written by David A. Wilson. I am of the understanding that "TAS" suffered a fire some time ago and this article is no longer available. With that in mind I don't think "TAS" will object to me posting it:" Guidelines For the Consumer...
IMPEDANCE.....PREAMP OUTPUT...........POWER AMP INPUT........
"HIGH"1.......OVER 600 OHMS...........OVER 100 K OHMS.......
"MEDIUM"1.....200-600OHMS.............20 K OHMS TO 100 K OHMS
"LOW"1........LESS THAN 200 OHMS......LESS THAN 20 K OHMS....
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1In DAW's opinion, no official standards exist."

I happen to come across some literature on the Audible Illusions L-1/3A preamps with output impedance of 1.2 kohms. Art Ferris designed them with tubes in parallel (thus halving their impedance),utilizing low-capacitance potentiometers,and increasing the preamplifiers current drive. Which prevents/minimizes high frequency rolloffs even with long cable runs.

I know Art has has his reasons but 600 Ohms is still quite a bit.