300B PSET

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.

Edoit,
If you do go the PSE route, Audio Note has two kits amps that are PSE. I haven't heard the PSE kits, but I have heard the kit 1 in my home and it makes music. I have heard two 300b PSE amps but have never A/B'd them with SET amps. Folks who have heard both say they give up just a little bit in that SET immediacy.

I have designed both SET and PSET and still make both. My experince, as mentioned above is that a well designed SET should not compromize dynamic authority. Less power should mean less bass.
PSET amps done right can provide the best of both worlds. You are still within the single ended topology but simply addition another tube in the mix for more output power.
as mentioned, the power supply is every bit as importnant as the circuit design. A great circuit is useless with a proper power supply just like a great power supply is useless powering an inferior circuit. You need BOTH.....

Missed a word above......"less power should NOT mean less bass".