i don't think you need any more fish. you're borderline overstocked already.
i don't believe in the inch per gallon rule/myth except to quickly determine if something is wrong. when you have more inches of fish than gallons of water you might start to get some problems with fish health, stress, territory and bioload issues, etc.
your common plec will get big 20-24 inches, your raphael and ID shark will get bigger, and tetras should be kept in groups of 6 or more to reduce anxiety and promote more natural behavior. also, though i am not positive, it may not be a good idea to keep tetras with angels as they are tasty treats for angels in the wild. when they get larger they may get more agressive and go after the tetra(s) as well as your other small fish.
don't add anything, and try to do some looking around on compatibility and stocking information.