Hard to say, fish are like people, you just need to get the right combination together so there isn't any friction. All depends on how big your tank is and how well it is decorated to break up the sight lines of the fish to keep tensions at a minimum. Tall, thick plant with rocks and caves are a good way to "break up" the tank.
And read the comment at the bottom, two severums can get agressive if they come at seperate times, it basic territory and it the same with angels you really should buy them at the same time too...
But with a heavily dense planted tank, you will be able to at least prevent excessive chasing and attacking of one another, because if you are lucky and you get a breeding pair of angels, they too will get aggressive to ANY fish, and will guard their eggs to the death...
You going to have to watch your fish closely, because these fish you have chosen are quite aggressive and may cause you more pain when you see the type of damage they can do to one another, and around here i know angel fish aint cheap either