Unfortunately, I'm using an Intel video card that Apple apparently got out of a dumpster somewhere... I should have invested in a better card when I got this machine four years ago.
I think you are simply out of luck, friend. Based on how you mentioned getting a card when you got the machine, it sounds like you are on a laptop, so it sounds like a new graphics card will not work as an upgrade for you. Even the 2D space sims I know about (primarily, NAEV) rely on a dedicated 3D accelerator.
Fortunately, the release of the 900 line of NVidia cards is finally dropping the price of 700 line cards.... slightly.
And I've read that AMD might have a new architecture coming out soon. If they can manage to push that through the door (honestly, the 970 fiasco would have been the perfect time to come out with something, ANYTHING new to take some market share away from NVidia, who needs the competition from AMD in order to improve better), it might reduce the price on AMD's R9 and even R7 lines. Again, slightly.