More power for better sound at low volumes?

What do you want the system to do better at low volume? Do you have an SPL meter to measure what you consider low volume?

A good set of headphones is your answer.

A lot of vintage gear used to have loudness controls and other tone control features that due to how the human ear works were useful at low volumes sometimes but required manual interaction to activate/use.

Its possible that this could still be part of an amplifiers design, ie internalized auto equalization in essence for the purpose of optimizing sound at all volumes.

Sounds like at least a couple makers might do this but do not know for sure. Some might advertise as a feature or some might keep it under wraps so as not to offend audiophiles that object to equalization solutions but like good sound at all volumes.

IF done well, I think this could be a good thing/feature if any makers want to fess up?

A Audio Research LS9 is the answer.

The fact that any good system sounds different when playing at low volume usually has zero to do with the system, and everything to do with your ears and your brain. The spacial cues provided by treble get lost, and the bass stops interacting with everything...clearly a good, even response system does sound better than a crappy one at all levels and obviously a near field system can play lower and retain fidelity because it's closer to your head. Remember, sound is made of waves travelling through the dense air in your room, to the dense brain in your head. I prefer that amp designers not put any low level frequency boosting in my amps, and I can reach for the damn headphones if I need 'em.