300B PSET

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".

Agreed that power supply is critical, after all the power supply is what you are listening to, the rest of the amp is just there to modulate the power supply to make a higher-power version of the input signal.

For example, my 833C SET amps have 400Joules of energy storage per channel in the output stage, and they are NOT limited at either frequency extreme. Yello shakes the walls and floor quite nicely, actually better than my previous 500wpc class D amp!