I believe the quote refers to the time period of the end of Voyager and beyond. I wouldn't put too much stock in it. It was just an answer to an offhand fan question.SF has a fleet made up of Sovereigns? Since when? Why haven't we seen these in the past? Shouldn't they have been used during the Dominion War? And if the rest of their frontline ships are all battlecruisers, then does that make the Prometheus a battleship?
Most likely it took a while to put the soveriegns and promethus-mkIIs into production. I'd wager they no more have fleets of soveriegns than they did of galaxies or other big warships. Most likely they Promethus and Soveriegns are used more as fleet flagships with lesser warships.
I'd say the Promethus MK 2 has something like the firepower of a soveriegn based on size. It might have more power if it retains the multiple warp cores. Then again it may not. There's no more than an offhand comment for information.
It's not canon at all. I'm merely pointing out that the super-promethus is not complete trekkie techno-porn. It doesn't exist on film. Put what faith you will on producer statements you will.I don't care whether or not any memeber of the production team said it; if Doug Chaing said the empire had a million Death Stars, would it be canon?