In case you were taking my thread as an example of how your 6800 GFX card might perform, the ATI 9250 that I was using is much below a NVidia 6800. You're at the higher end of recommended hardware with your 6800 and much more so with the rest of your system.

I should add here that later on after upgrading my GFX to NVidia 7600, I noticed that my CPU needed one step up in voltage... about +0.1 volts (OC'd cpu's have a bigger appetite for voltage). Had I noticed that while using the low end ATI 9250, the system as a whole may well have performed better than it did in terms of stability.

I'm very happy at the moment with my 7600 gfx, 512 MB ram, and mobile xp2500 (OC'd to about xp3000 or so). I haven't tried running the resolution higher than 1024x768 because of the quality of my monitor, but I'm sure the gfx would handle higher res too. Works great with FSOne.

Like stated in the above post, there can be subtle issues with drivers, etc. Make sure to update everything and check that the system is running properly overall for best performance.