I can, after listening to many different types of speaker system, endorse only one. They were given to me by the father of a good friend of mine. He bought them new.
These are of 1960's vintage. I have been using them with the 7-tube Magnavox amplifier, whose schematic is shown here. I consider them a very good, first-class example of the types of speakers best suited for use with tube-type amplifiers.
Above, a picture of the Jensen PR-300 cabinet with optional leg set.
Above, label on the back of cabinet. Click to view fullsize. I have found very little on these fabulous units on the internet. I cannot comment on how common or rare they are, but I feel very privileged to have this pair.
I am showing these speakers here as an example of what is recommended for use with the tube amplifier designs presented here.