Bah I just lost a long post but here it is, Gal civ 2 is good unfortunatly no tactical Battles, battles just are determined by computer and their a simulation of the results.
HW 1 and 2 are good. Its real-time 3d stratgy.
Spirutal successor is Sword of the stars.
Game I would look at is X3 "reunion" , it is more a space simulation you fly your own ship initialy and can be mercenary or trading. But you can build mines on astroids and sell the goods, and even buy other ships to make a fleet and have the pc do trade routes and so on. Economy is very complex. Game is like Elite or Privateer.
One thing to note is it has starforce copy protection, but if you get it thru steampowered.com , it dose not have starforce.
Space rangers2 is another game to look at though it like a space control game with all 2d top down , adventure game. It unfortunaly also has starforce, though think maybe a version is out that dosen't have it.
Last game you may want to look at is hte battle cruisers serise its a old game but the creator made it free to public after 5 years. YOu can check them out here
http://www.3000ad.com/downloads/index.shtml
I couldn't get these to run on my newer pcs .