SS. Amp to go well with Aesthetix Calypso Preamp.

Not true Russb. Here is the quote from JA's "Measurements" section of the Calypso review.
"The balanced output impedance was 112 ohms at 1kHz and above, this increasing to 3900 ohms at 20Hz due to the finite physical size of the output coupling capacitors. The unbalanced output impedance was a high 2400 ohms at midrange and high frequencies, rising slightly to 3150 ohms at 20Hz. In unbalanced mode, the Calypso will need to be used with a power amplifier offering an input impedance of at least 30k ohms if the bass is not to sound lean."
The trouble with many tubed preamps is the output capacitor size is limited which results in an increase in output impedance at low frequencies. Based on my experience, I would recommend a ratio of at least 20:1 of the amp input impedance to the (maximum) preamp output impedance. However, if you do not have full range speakers, or are not concerned with a low bass roll-off then maybe this would not be an issue for you. I will say the Calypso did not do much for me when run into a McCormack DNA 500 (input impedance of 10K ohms).

Bob reynolds; the 40K assumes you subscribe to the 10:1 minimum ratio camp, and would probably be fine in many cases. However, after trying a whole bunch of preamps, I have found better luck when the ratio is higher. One can review the potential effect for their own specific equipment by looking at the dBr vs. frequency plot and interpolating for their own given amplifier load. The 3,900 ohm reading is at 20hz, so one might find a small drop in output at low frequencies is acceptable, especially if they are using monitor speakers, or speakers without much output below 35-40hz, since the drop at the speaker's low output limit frequency may be smaller than the drop at 20hz. Personally, if I were to use the Calypso with a SS amp, I would try to get something in the 80-100K ohm input impedance range, such as the JC1 monos which I believe have 100K ohm input inpedance. Ultimately, the main reason I sold my DNA500 was to be able to try a wider variety of tubed preamps without being handicapped by the 10K ohm input impedance.