As someone who started out with tube experience in guitar amplifiers I have always found EL-34s to be a good tube to drive to power tube distortion in a cranked Marshall amp. They lack bass compared to a 6L6GC.....anyway never have been interested in them for hifi stereo.
I have a chifi 300B/845 amp (Muzishare R100 845) that I tried out for a while. Definitely more bass punch than SET 300B amps. But the heat that thing thru off could heat the house and too much in the California climate. And I did not find it more resolving or any other benefit other than more power. (I will gladly sell it if anyone wants and amp around 100lbs!) It's basically dual mono blocks fit into a single chassis (4 transformers).
For 300B I ended up with the Icon Audio Stereo 300 MKII which employs a quartette of 300Bs in what I believe is parallel single ended mode adjustable fixed bias...not sure maybe it is some kind of push-pull...have not seen a circuit diagram. The manufacturer just says the 6SN7s run is cascode mode.
Well it has plenty of power and good grip on the bass. I use it with Klipsch Forte IVs and rarely turn it up past 10% unless I want my wife to start yelling at me.
I think there are a few other 300B quartettes out there...maybe Cayin. Check them out. I prefer to the larger space heater 845 or 805s (you need to add solar panels on your roof to run them unless you want to pay $1k for electricity every month).