There are no really special requirements for my angelfish tank. My 55g once had a small group of wild type angelfish as the main fish. I kept the temperature at about 78-80, KH 4 and GH 5 out of the tap. Relatively dense plantings. They love slender, grassy plants such as Cryptocoryne balansae, retrospiralis, spiralis, and Vallisneria sp. They also appreciate broad leaved plants like large swords to lay their eggs on (a good sword would be the more moderately sized Ozelot).
I would buy a group of six young specimens and grow them out, letting them pair off. I wouldn't house six full grown angelfish in anything smaller than a 75g though.
Good companion fish include blue rams, corydoras catfish, and moderately sized tetras such as Black Phantoms (M. megalopterus).
Thanks, that helps. They are a fish I've wanted, but never been sure about getting. I don't have a tank suitable for them right now, plus I need a bigger house or in the very least a fish room. Oh, well I can dream.