I don't think the 50K ohm figure is correct. Perhaps they meant 5k ohms.
In any case, with a 40k ohm input impedance for the SE-100, most tube amps will work, IMO, including the Cary SL-98p that has an output impedance that rises to 6.8k ohms at one point (according to John Atkinson's Test Measurements section of the Stereophile review).
In any case, with a 40k ohm input impedance for the SE-100, most tube amps will work, IMO, including the Cary SL-98p that has an output impedance that rises to 6.8k ohms at one point (according to John Atkinson's Test Measurements section of the Stereophile review).

