I'd be more concerned with being overstocked, that's a ton of fish. What were the tank dimensions again? I'd be less concerned in a 48x18 75g but even then that's pretty heavy.
your going to be way overstocked if you add another school, I'd reccomend trimming down to either the angels or the GBRs. Then I would get 10 panda corydoras, and be done.
Beautiful tank!
I'm not sure I'd add cardinals or neons - won't then end up angelfish snacks eventually? I'd get 10 more rasboras and see how it goes for a while.