But that kind of power is not harmful because pretty much the only way you can acquire it is by giving others what they most want. That's what will be compensated with wealth.
You've made a mistake here because the two are not related in the way you're implying. A process (giving a subset of people what they want) which provides an attribute (power) is a cause and an effect, but it implies nothing about what one can do with that power (such as make life miserable for any other subset of people or, even worse, cease giving others what they want and simply wielding one's power).
OK, let's say you're the richest man on the planet, in an AnCap society, Bill Gates, Warren Buffet, and Carlos Helu all rolled into one How do you wield your wealth so as to make others miserable?
You're right, of course, that the Non-aggression principle is sort of a "ground floor" of libertarianism, while self ownership is the foundation. But just like a house, you don't need to see the foundation if the ground floor is sound. Sure, you can look around in the basement if you like, and any decent tour of the house is going to include it, but for most people, the ground floor is enough.