300B PSET

Edoit,
I have to suspect this is speaker matching related rather than a case of lack of power availability. I've heard enough SET 'single' tube 300bs to know that these frequency extremes are present(with a properly chosen speaker). Depending on the particular speaker in question(load/characteristics) a PSET could certainly be the better choice.You really must view the amplifier and speaker as one entity (inseperable pairing).There are listeners who obtain full frequency sound with 2 watt 45 SET amps if using an appropriate speaker.
Charles,

I agree with Charles. Also as he implied, not all 300b SET amplifiers are the same; and not all 300b tubes are the same.

Edoit, Do you have speakers in mind?
Jet

I auditioned trenner and friedl speakers with 93 db and 8 ohm with verdier 300B. Bass was there but 845 mono blocks driving same speakers gave better low frequency extension. But I like 300B for the magic it does to midrange. That brings me to the question, will a parallel 300B have the best of both worlds using the same speakers?

Edoi,
I like both 845 and 300b SET amplifiers, I do understand your attraction to the 300b attributes. A PSET 300b could be an ideal compromise with this speaker.Some 300b SETs with identical watts/power ratings will still vary significantly in bass and HF performance due to design, power supply and output transformer quality.I like your taste in speakers by the way. Generally speaking the 845 will provide very good bass and drive. The 300b perhaps a bit more nuanced and intimate(there's much overlap between these two tubes in reality due to implementation).
Charles,