300B PSET

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,

Charles mentions power supply and output transformers. Try hearing a SET 300b amp with a beefy power supply like a Border Patrol SET 300b amp. You might find this amp gives you the bass control that you seek. If your like me, once you hear that SET mid range magic, you'll have a hard time living with anything else. A SET amp with a well implemented power supply may be what your looking for.