Best 300B SET

Have to agree with Gsm18439(Gary). There are no shortage of worthy canidates in this realm. System matching and individual listening preference make it impossible to declare any of them the best. You can certainly say there are a variety of superb choices available.Those SETs listed above would qualify.
Charles,

"Looking for 300B SET (one output tube per channel)"

Do you mean one output tube per channel as in you don't want PP, or do you mean an SET with 2 output tubes, or both?

Not sure what your speakers are but you might look at Sophia Electra, they have a couple of versions of a stereo version as well as mono blocks, and a company called Japanese Triode has a nice set of mono blocks, the TRX-M300 .

Go beyond the obvious….

WAVAC, Mastersound, VIVA, Line magnetic all make wonderful 300b amplifiers of extreme quality.

Johnk is correct.