Thanks, guys! I'll look into these. Just a question: Not incorporating my original posts about expansive worlds and stuff, in general how good are the Wing Commander games, Inependence War 2, and freespace 2?
Independence War 2 is very much in the vein of what you are looking for. I-war 1, Freespace, and the Wing Commander games apart from Privateer (which is also in the vein of what you want) are very mission-based military space sims. They are all very good, but not quite in the vein which you specified. You sound more like you want an open-ended, exploration-based space sim so I would go with Independence War 2, Wing Commander Privateer, Star Control 2, or Space Rangers on GOG or the X3 games for a newer series of games on Steam.
I-war 2 has the uniqueness of also having a newtonian flight model which is very cool and from reviews both pro and user it seems it does not have loading screens for when you travel from place to place in a very big galaxy. It's on my backlog to play. :) While it does have installations that you can dock to, I don't think you land on planets or you control your character physically walking around in the space stations. All-in-all though, the game hits a lot of the points you are looking for - action, seamless travel around the galaxy, expansiveness, open-endedness, etc ... Gamespot Review