Hortlund, you only need more than 512MB on the Finland map- and at any rate I honestly do not believe _ANY_ graphics card has enough on board memory to handle the city textures of Leningrad and the outlying fortresses of the city.
It's the biggest resource hog and apparently the beta testers didn't take into consideration the need for lots of repititve low detail city textures rather than lots of individual high detail textures and this leads to lots of lagging as textures are transferred from system RAM to video RAM.
Be sure to select the GF2 settings on the video tab, THEN go back and select custom from the drop down menu. Where it says "texture compression" select S3TC from the drop down menu. This should help quite a bit.
I'm not sure with the GF2, but with my GF4 32bit is faster than 16bit because that's what it was optimized for. However, I believe people have better success with 16bit using the GF2. 1024x768 is supposedly the optimized resolution for Il2/FB.
My system isn't much higher than yours, it's an AMD 2000+ running 768MB PC133 SDRAM and a GF4, and I can run the game at full details in OpenGL EXCEPT for perfect water. Don't use the stencil buffer, it'll slow your system down dramatically.
-SW