AMD Athlon 64 X2 6000+
4 GB DDR2-RAM (though only ~3 GB are usable due to 32-bit OS but whatever...)
BFG GeForce 8800 GT OC
Running on 1680x1050 resolution, I can use everything that the community has to offer... plus some of my more insane contraptions like a 4096^2 mipmapped starfield so that I can use smaller fields of view without blurring the starfield.

It gets better though, for I am capable of maintaining generally playable (+30) frame rates with 32xAA (anti-aliasing), 16xAF and optimizations aka quality degraders turned all off. With 8xAA, the frame rates usually stay well above the hardware limitation of 60 FPS which is the highest my screen can do. The only problem I have is the insidious thruster trail flecks if I use anti-aliasing.
Sololop: Yes, when it runs on one core it's only using half of the processor's computational capacity. However, actually getting advantage from multiple cores requires the program to be designed for threaded computation and FS2_Open... is not. And will very very likely never be either. Most programs still aren't. The benefit from multi-core processors is at the moment mostly that you can run two CPU-intensive programs much better than on single core, and applications using single core are less likely to jam the whole system if the application hangs since the other core is free to operate system requests (or something like that).
Moreover I would say FS2_Open doesn't really need to be ever optimized for multiple cores either, because the power of individual cores is very well enough to run the game smoothly, it's the graphics renderer (and memory in older PC's) that become bottlenecks to cause FPS drops. And converting the game to use threaded processing would be... unrealistic endeavour that would likely end up in violence.
