I really don't believe that a Rock Beauty and a Powder Blue should be put together in that size tank. They both really need 125+, or a 6' swim length. A Powder Blue is a difficult fish to begin with and the stress of the smaller tank, combined with the semi-aggressive nature of the angel will more than likely be an issue. Not to mention the bioload of these two fish. I would X the Powder Blue, but if your determined to have one, make it the last fish you add. You'd be better off with one of the larger Dwarf angels to be honest, the 2" will make a difference in a full size fish, especially when discussing how much swimming room they need, dwarfs stick to rock work much more and weave in and out while the larger species come out into open water to swim and really prefer the 6' long tanks. Also, as a general rule, Powder blues do not accept other tangs, especially in smaller systems, and the Kole, being a much more peaceful tang, would get beat on.
Have you researched the dietary needs of a Rock Beauty Angelfish? They're difficult to keep in a home aquarium and many people don't have luck with them.
Hope this helps, making a stock list can be so tedius! Interested to see what others have to say, especially AquaKnight, he always has excellent advice about stocklists.