I think what the OP is asking is whether he should get his pajama cardinal and his ocellaris each a mate of their own species.
In the case of the clown, I'd say go for it, as long as the new ocellaris is either bigger or smaller than your current clownfish.
With the cardinal, you might be better off keeping a small group (if you have a good-sized tank--55G or more). I've kept pairs or trios of pajama cardinals before, but the male tended to pick at the females if they got too close to him. But since they weren't truly aggressive to each other in the way that Banggais are, I think they might have been fine in a larger tank.