Personally I'm such a fan on butterflies I would happily keep a corallivore in an sps dominated tank because honestly they're worth it :) It's rather unfortunate that my two favourite families are butterflies and angels and both are coral munchers and I love sps, oh what a dilemma :P
I have multiple angels in my little 2ft cube :) A female gencanthus bellus and a yellow tail pygmy angelfish :) I adore both of them and they get along really well. If they've got enough room and you add them at the same time and in the same size I would think you'd be okay, I haven't heard much about angels being overly aggressive with each other unless is dwarf species :)
