The power of preaching is the Holy Spirit using the public reading of the Holy Scripture with nothing added. Yes pastors talk thereafter, but their talking is likened to the movement of the priests. The priests had to move inorder to sprinkle the blood on the altar, but the power was not in their movement, but in the blood.
God is so Sovereign, that like Philip, God could cause me to appear in another place, like North Korea, and with one sermon like Peter, God could regenerate the entire political and military membership, though I have never studied a syllable of the Korean language, nor have access to a translator.--and all with the same ease as the centurion admitted:
Mat 8:8 But the centurion replied, "Lord, I am not worthy to have you come under my roof, but only say the word, and my servant will be healed. 9 For I too am a man under authority, with soldiers under me. And I say to one, 'Go,' and he goes, and to another, 'Come,' and he comes, and to my servant, 'Do this,' and he does it."