cathode-follower tube preamps..

I think you are going to find CF's in most of the tube preamps you go looking
for. It's not the spec I would go looking for.

fwiw, I have 2 Pass amps (30.5 and 100.5's) and I drive them with Conrad
Johnson tube preamps (ART and ACT 2.2) and neither of them have CF's. Their
output impedance "averages" 500 ohms and is not a problem for me. My Pass
amps are rated at 20K or 30k (rca or balanced).

Whatever the input impedance is of your Pass is, just look for a preamp that is
at least 1/10 of that and hopefully a little more because the output impedance
does vary at different frequencies. That spec is just an average.

If you have a direct-coupled output on the preamp the output impedance will not vary with frequency (with most tube preamps its usually the bass where this is an issue).

If you have a 10:1 ratio at 1000Hz but only 5:1 at 20Hz, you will hear that as a loss of bass impact. This is because there will be a slight loss of output voltage in the lower frequencies.

Belles VT-01. $4,700

Is CJ ET3 SE a good choice?

To answer your original question...try Mystere CA11 or CA21 preamps. The CA11 uses a SRPP (Series Regulated Push-Pull) circuit for high gain, low distortion and very low output impedance by using a variation of the White Cathode Follower. The circuit uses no negative feedback for more natural tonality.
http://mystere-usa.com/index.php?option=com_content&view=article&id=91&Itemid=167