First, doglover, welcome to Tropical Fish Keeping forum.
Now, on the angelfish. We have profiles, second tab from the left in the blue bar across the top of the page. If you check that for this species, it mentions that they are a shoaling fish that should be in a group of 5 or more [you could manage with 4, but five is better] unless you have a mated pair. It also notes that adding more to an existing fish/group can be risky; I won't repeat what is in the profile. You can see the profile if you click the shaded name in posts, and if the name is identical to that in the profile it will shade, example Pterophyllum scalare or Scalare Angelfish.
Now to the tank and stocking. As others have noted, there are some issues here, and if I were you I would not compound these by adding more angelfish. The barbs, tetras and rasbora listed are all shoaling fish, meaning they must be kept in a group. You can check all this in the profiles, all species are included. So the first thing to decide is, just what you want in this 55g tank, and work toward that. Some fish may have to go, and more of the ones you want acquired. The knifefish is obviously going to impact on this.
I don't like suggesting what one should or shouldn't keep, it is after all your aquarium, but my concern is the health of any fish you do have, and providing the best conditions for them. So if you have further questions after you check the profile data, don't hesitate to ask. We are all here to assist.