Help, which preamp to buy from my shortlist?

1. Evaluate how well you can hear.  %IMD, %THD etc.  No sense in getting equipment excessively better than that.

2. You will go further powering your pre with a power regenerator. Not a filter.  A $1500 regeterator is like a $10 preamp upgrade.  See for yourself

You might add a GAS Thaedra (with a GAS Audio rebuild) to your list.  

I have a Sonic Frontiers SFL-1 I bought as a back up / maybe for another room.... When they came out I was newly married, kid, house, and all the bills that went with....so fast forward 25 years and I bought one for a good price.  Great preamp for sure, still supported by Parts Connexion.     

I just bought a Zesto Leto preamp and am actually going to keep the SFL-1 for another room and sell the CJ Classic 2SE that I'm replacing.   

Avoid the Meitner PA-6. 

a friend's Meitner PA-6 failed, unrepairable RC circuitry rendered it a $$$$ paper weight!  He loved the SQ but...

"What?  No ARC SP-6B?"

Not on the OP's list.

"Where's conrad-johnson?"

Not on the OP's list.

The question is "Why aren't these on the OP's list?"  Maybe they should be since, particularly with the SP-6B, these manufacturers typically built pre-amps that outperformed those that are ON the OP's list.