My system specification,
core 2 quad 2.66Mhz
VGA 8500GT 128Mb dedicated (~1000 Mb shared)
I tried to play Arma 2 with the above machine and frame rate is very low to play even the menu does not load properly. Then I removed my 8500GT and tried with my onboard VGA and I have same performance. But I think that I should experience little more framerate with 8500GT. Am I correct? Arma 2 require Nvidia Geforce 7800 But I have 8500GT. I think that 8500GT is higher than Nvidia Geforce 7800. Correct me if i am wrong. Does this have something to do with the other parts of my machine? Please explain.
7800 is better than the 8500GT. It was the top dog when it came out a generation before the 8xxx series. The 8500 is not a good gaming card the 8600GT was considered close in performance to the previous generation 7600GT.
Arma 2 is known for have very poor performance anyhow. Go check out the forums for the game. Even folks with the latest high end video cards complain about poor performance. Really pretty sad because it seems to be a pretty good game.
I tried playing it with two GTX 260's and one particular level was so horrible I couldn't finish it. So I had to stop playing the game.
If that's your budget and the price difference is what you say then you should be looking for an HD4670 or 9600 GSO. They are pretty good gaming cards for low resolutions(1280x1024 and below.)
Look for a DDR3 HD4670 rather than DDR2 but ignore differences in memory size(512mb vs 1gb) because the card can't effectively use more than 512mb.
For the 9600 GSO there are a lot of different varieties. Some are good and others are pretty bad so ask here before buying one.