The Meaning of Life, the Universe, and Everything.
Everywhere and nowhere.
I used to have 4 space and it was ok. I have looked at a couple of other addons but the one that really caught my eye was Galxay Space. It adds the rest of our solar system with dwarf planets, moons and other asteroid belts. It also adds more solar systems. For the most part it is based on scientific stuff and has a couple of fun stuff in it. But it is super close to what a more "completed" version of galacticraft would possibly look like. Check out its minecraft forum page. Also it is a WIP.