Thing is, GalCiv2 is more CPU intensive, than graphics.
I have a 2.8GHz Pentium D with 3GB of RAM, and a 6800GS PCIe video card with 256MB. Not the latest or fastest; it is 3 years old after all.
GalCiv2 is stable and fast. I have zero problems.
I can make the game crash, if I really try. All I have to do is destroy several hundred enemy ships, then invade 25-30 planets - in a single turn. (which is why I save the game often during such a turn)
popsursocks problem may be due to outdated drivers, or a bad download, or background processes that are running (always remember to exclude the GalCiv folders from your real-time virus scanning - both in Program Files and in My Documents), or using Impulse to update instead of Stardock Central, or the resolution mismatch, or simply that version 1.0 is buggy as all hell.
It is not due to a 6x series Nvidia card (or an FX-5200, for that matter). The 5200 is not DX9.0c compliant (9.0), but the 6x series is.