I know that this isn't quite what you meant by clash of space ships and interstellar battles, however it's also always great to expand your horizons a bit, as long as the games are good that is
Freelancer: Is a great game that you are a... well... freelancer pilot. There are a multitude of factions in this large galaxy with multiple systems and planets for you to go to. There are also a multitude of space stations to explore, factions to work for, trades to make, and almost any other job you want including bounty hunter work. Also you can trade, buy, sel, upgrade and outfit your ship throughout the game. After you're done playing solo, you can go to online servers and the game plays similar, except without the single player story, and with a bunch of other active players who's intents are unknown, however you can still make allies, allegences and enemies. Trust me man, I was hooked on this one for a good while.
When or if you finish that one, there is another game called X3 (no, not X-men 3, lol) It's along the same lines as Freelancer, except the single player is far larger and technical in about every aspect, and there's a good amount more to do (and Freelancer was big to begin with). Also the graphics are WAY better then most space games. However there is no online play, but if that's fine with you then it's definatly worth checking out.
By the way, each of these games are under $20USD which gives you a LOT for your buck. Trust me ^^
*This post has not been spell checked*
Jam it back in, in the dark.