It was hinted that Princess Celestia's power dwarfs even that of Queen Chrysalis. Had the Changeling Queen not been super-charged by Shining Armor's love (not surprising, given that positive, communion emotions like friendship equals magic in Equestria) she would had been crushed like an insect.
Oh totally. When Celestia first walked up it looked like Chrysalis might have been having an "OH CRAP I FORGOT TO PLAN FOR THIS PART I'M GOING TO DIE" moment on the inside. Changelings really aren't a good source for power comparison. I imagine they're not terribly consistent depending on who they're feeding off of at a given time.