What are you running for a monitor?
A better video card with higher performance video memory will primarily allow you to run at higher resolutions and color depths. Your CPU is going to have to generate a lot of the math anyway, so your FPS in a given situation may not change a great deal.
Basically, I got framerates that were just as good as my V5 with my old V3. The difference is I went from 1024x768 16 Bit to 1024x768 32 Bit and 2xFSAA. In image quality the difference was HUGE, while still retaining nice playable framerates.
If your monitor is good enough, you should be able to use higher resolutions with the new card, and if not, you may be able to run FSAA and get better image quality.
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Sean "Lephturn" Conrad - Aces High Chief Trainer
A proud member of the mighty Flying Pigs
http://www.flyingpigs.comCheck out
Lephturn's Aerodrome for AH articles and training info!