I like Fading Suns a lot myself. It has all the tech, psi, and even magic accessories to play space opera in whatever setting you design. You can drop psi and magic if you don't like them.
Spaceship construction is very simple, sometimes a little too simple for my tastes, but it's rules light nature makes investment in understanding it minimal. It's stats are for very lightly crewed vessels with a very limited number of weapons.
FTL travel is by emplaced warp gates. A gate drive is required to utilize the gates, so you can drop the gates if you want and replace the gate drive with a warp drive, hyper drive, jump drive, stutter warp drive, or what have you using your own parameters of travel rates and speeds.
There is no meaningful star/world construction system. You'll have to pull from another game to do that. A lot of space opera may not require detailed star system and world construction.
For Star Wars games, I just make star systems up on the spot and who cares if an O-type star is only one in three million and can't grow planetary systems because of stiff solar winds and supremely short lifespans? I have a string of them and put some planets in their far orbits and slap down some with hardscrabble biospheres of cold ice or blazing heat (favorites), pirate hangouts, communities that have deliberately become lost to knowledge to keep the privacy of their inhabitants, fanatic religious monasteries, and equally impossible Oort clouds full of miners who utilize the pirate hangouts more than the pirates do. Oh, and a crazy Jedi just to keep things interesting.
For more science-oriented games, that's not so easy to pull off in a few easily worded phrases, which can make full star/world constructions systems very nice.
