What actually determines volume power? Is it watts?

My guess is that this amplifier is thinning out at high volumes and can’t keep up with the demands of the music and the speakers. A high current amp of the same wattage would probably sound fuller at high volumes and might scratch the itch. I would look for a 150-200 watt minimum amp that doubles its wattage from 8 to 4 ohms, and is stable into 2 ohms. Coda, Pass, Krell etc.

As long as you aren’t straining or clipping the amp, it makes no difference where the volume knob ends up. As a matter of fact, you want to be using the least amount of attenuation for best sonics.

Many people conflate gain and power. You could buy a different amp with even less power that gets you to the same volume level at 50% of the range. If you can get to the level you want with your current amp by using most of the 30% of the volume control you have left, you don’t need a different amp.

You are worrying about something that shouldn’t be worried about.

Knowing the speakers will likely make this thread more informative, and thus more enjoyable (for me anyway).

No system logged in profile.

First and foremost, it would be helpful to know if the OP has ever undergone an audiometry evaluation and what the results were.

Let me third the question: what Speakers?