Rebekah Lux Aikaterine is my favorite of your choices, but they all sound more exciting than my own middle name. Mine is
Rebecca Ellen. My great-great-great grandfather was a
Levi, a name I also also like. I think
Orion works nicely with
Levi. I might be inclined to choose a Biblical name to pair with it, but I still like
Orion.
The popularity of my name has really dropped a lot since I was born, and I think it will probably keep dropping for a few decades. I doubt it will ever go below 200-300, and it will most likely come back up eventually. The spelling
Rebekah will probably always make it lower on the popularity scales, but it's still the same name. I've heard people refer to it as the "Biblical spelling," but really it is the translated spelling of the original Hebrew that the text of
Genesis was written in, and the Hebrew name is
Rivka. the "kah" version is just an older English translation of the Hebrew name, and the "cca" version is more recent (still many hundreds of years old). How you spell it is just a personal preference as a parent. I only felt the urge to have it spelled with the kah ending once when I was about 8 or 9, and I soon figured out that it didn't make me any more unique since it still sounded the same. I went straight back to cca because that is the name my parents gave me, and I was used to it.
Nns... I hate
Becky. I have a few friends who call me
Becca, and only one person has ever called me
Reba. It didn't feel right. Generally, no one calls me by any nicknames, I'm just
Rebecca, and I prefer it that way.