The trouble is, most in print d20 Sci-FI games are just frameworks. The only real exception is Dawning Star, which has 2 books and some others, and while I like that, it's pretty much set in one star system. (It's also expensive to get into if you don't have D20 Modern & d20 Future, although the latter isn't a must own)
Bulldogs!, which I liked, is mostly rules in its book. There is some setting info, but really, not much, most of it is in small sidebars. It's a very good stand alone sci-fi d20 game. Yeah, it's based on 3.0, but most of the changes to 3.5 were in magic and classes and such and don't impact it much.
T20 I think has some PDF supplements. But it's such a mess as a game, I wouldn't recommend it.
Fading Suns d20's corebook is quite good, but the d20 supplements for it are of poor quality (the ones I have) when it comes to d20-ness