Then it sounds to me like you are listening to a lot of bands that sound like Dream Theater... Not that bands sound like them. Progressive rock is more defined by it's continuous musical movement, different time signatures, keys and modes. That's the progressive part, and of course rock is the other.
Power metal is more melodic, not having anything to do with the progression portion. Power metal is more of an 80's style, now you have more variations - hardcore, grindcore, speed, black, etc.