I would think a 55 would be ok by adding two fish at first.
The general rule it to add the most agressive fish last.
Now the problem is trying to figure out which of the 4 fish listed is the least agressive.
Personally I have not seen my coral beauty have agression. Its always been a very passive fish when it comes to feeding times and just general swimming around and does not pay attention to the others. As kevin said some pygmy angles can be more agressive.
I am only speaking from my personal obeservations and also the angel was not the first fish in the tank.
Clowns can be agressive but usually toward their own genus more than other fish. In a tanks smaller than a 55 putting another fish in with a maroon clown could be death for the other fish. If you have a 55 gal
with a fair amount of LR
a clown first should be ok even if it is a maroon.
I have no experence with either tang or flame hawk. I do know the tangs have a sharp bone just infront of their tail they use to defend themselves but dont know if they tend to be overly agressive with it.
Have you thought about two clowns? Two small clowns would be a good pair of starter fish.