Impedance Matching Preamp/Amp Assiance Pls?

It is not unusual for tube preamps to greatly exceed their reported (at 1K hz) output impedance at lower frequencies. This can be heard as a bass roll off with some match-ups, usually into SS amps with input impedance below about 20K. John Atkinson provides useful information regarding impedance matching in the "Measurements" section of Stereophile reviews, and here is what he said about your SLP 05, in Sept of 2006:
"The SLP 05's output impedance is specified as a usefully low 400 ohms. However, I got significantly higher values for the unbalanced output of 1500–1600 ohms in the midrange and treble, rising to 3400 ohms at 20Hz, with similar if slightly lower figures for the balanced output. The Cary preamp needs to be used with power amplifiers having input impedances of 10k ohms or greater if the bass is not to sound a little lean."

Saki70, you are welcome. I am glad to help with things I have learned, as many others here have helped me along the way. To Nick778, I am a little surprised at JA's comment about using the Cary with amps having input impedance of at least 10K ohms. I consider the 1:10 ratio recommended by many to be a minimum at the lowest frequency where your speakers provide useful output. Personally I prefer a ratio of about 1:20 or better when possible. Since the 05 was measured to have output impedance of 3,400 ohms at 20hz, I would probably look for an amp having input impedance of at least 47K ohms (seems to be a common input impedance) to use with the 05, and I believe your Spectron amp at 50K ohms should work fine.