Do I really need a preamp?

Yes, George, John may well have stated that. I gave up believing everything I read in Stereophile decades ago. If a tube amp the input impedance can be set almost arbitrarily but most manufacturers go with 100K and I have seen some that are as high as 1 Megohm.

For solid state, 10K is usually the bottom end of the range and 100K is the highest, most likely an amplifier with FET input. Dynaco built their PAS3x to be able to work with 10K. ARC OTOH does not expect to see less than 30K with their preamps. We build our 2 bigger preamps to be OK with 600 ohms and our smaller preamp is good down to 10K.

Bottom line is its all over the map, Stereophile notwithstanding.

When researching SS amps to go with my current ARC tube pre-amp, I found a surprising # of leading contenders otherwise with 10Kohm input impedance or not much higher, especially older models. The trend in more recent years might be different,perhaps due to popularity of tube pre-amps with audiophiles.

Most that mentioned design for use with tube pre-amps tended to be in 60-100kohm range, unbalanced, double that for balanced.

Mapman, then does that mean if my solid state amp has an unblanced input impedance of 47K ohms that it is not compatible with a tube preamp?

Any input impedance is "compatible" ie it will work. Its more a question of how well. The 10X rule is commonly cited. That's a reasonable approach, the challenge being that impedance can vary widely at different frequencies and a single output impedance rating may not reflect the worst case, so I think it best to include some tolerance as an insurance policy whenever in doubt.

47Kohms is most likely a good match in general. I would not be concerned at all if everything else looks good. I cite 60kohm merely as a very safe number to go by in most any case based on what the vendors seem to commonly go for when designing towards the goal of compatibility with tube pre-amp gear. Higher input impedance is pretty much always as good or better for best results in regards to low distortion, detail and dynamics.

YES it is the heart of your system