Impedance match

What I mean is (and I do not consider myself a typical component purchaser is: this topic has never been explained or mentioned in any component manuals

I have probably flipped through 10 preamps/amps in the last 15 years

I can't help but wonder how much it had to  d with impedance mismatches 

I think the concerns around "impedance mismatch" are somewhat exaggerated for most "typical component purchasers". By far, most of these purchasers either buy an integrated amplifier/receiver or solid state separates where the (separate) preamp almost always has an extremely low output impedance. Tube electronics, particularly separate tube preamps could pose some matching concern but those are usually purchased by more demanding, and sometimes more knowledgable  customers.

Matching concerns for all passive preamps is even more critical, if one doesn’t get at least a 1:6 ratio or higher from source to input and from output to amp then the wrong conclusions will be drawn about passives and the way they sound.

If done right they will give more transparency and better dynamics than preamps can hope to give. And save you a great deal of money as well by not buying $$$$K active preamps.

Better still is going direct if your source has a volume control, but there are things to look out for here too. As well as hearing your source without preamp colourations, you may not like it's sound, as it's ruthlessly revealing and dynamic.

Cheers George