The 10g per angel is a pretty good number to work with. The water quality still has to be there for them to grow properly. But what you have should yield normal and robust angels.
But you'll be faced with the usual dilemma as they grow. One or more pairs will form and things go nuts. They are cichlids, make no mistake about it. Yes, this is thinking ahead, but it's just part of the process that you have to be prepared for. With six fish, even I would bet you'll wind up with one pair. There will be aggression that will last right up until the spawn ends. So you'll see the aggression come and go. The key is to have a plan in mind for when you come to that point.
"Why can't my wife see all of this stuff as an investment?"