Actually, if we're going by the original book the movie is based on, Sadako can manifest herself in any reflective surface. It's just for the movie that they had her come out of the TV to add some weirdness. Kayako isn't really bound to the place where she was murdered either. She can been seen in many places during the movies.

And well, Edda isn't really creepy, but neither is Sadako if you know her backstory. Kayako on the other hand is pretty vengeful though, but it's somewhat understandable.