I'm so glad to hear you've got crowing!! I have a couple of 3 week old roosters (jumbo browns) that haven't started crowing yet but I'm excited to finally hear them! Maybe that means they'll start soon.
I have to agree their fist crows are pretty pathetic sounding. They have the concept but haven't mastered the "Look At Me".
Ours began crowing at about 4 weeks. After a few days it was ALL NIGHT LONG due to the Security Light outside the living room window.