I have a simple question: Would an 8800gts 640mb be sufficient for running the game at decent (Medium texture, no AA or AF) settings at 1680*1050?
ArmA is a complicated beast in terms of performance, noone seems to be able to get it to work 100%. It also suffers from real issues with the 8xxx series in general.
Some of the issues with 8xxx cards specifically;
- LOD issues, objects and textures don't scale to detail as you get closer to them, so you end up with soldiers standing around you made of leggo.
- Over saturation of visuals, like picture a TV with the contrast turned up ridiculously high.
- Thick white fog rim which seems to sit at a set distance no matter what you put your view distance on.
- Shadows only rendering when you are extremely close to objects and also occasionally rendering as solid cube shapes.
- Crash to desktop with a certain error code.
- Questionable performance.
In short I'd say if you were looking for a graphics card to run ArmA well pick up a 7xxx series card, like a 7950GT. As even the developers have said that ArmA doesn't work well with the 8xxx series. Also from what I have seen on the forums people with high end 7xxx cards seem to have the best performance.
Personally I've got an 8800GTS 320 and it is a great card which runs all my games beautifully. However I get a lot of the problems fellow 8xxx users experience in ArmA at random, that is except for the over saturation and crash. Like I get LOD scaling problems, I have the fog and I randomly see shadows rendered as cubes. I also find my NVG's flicker and stop working at random, which means night missions are basically not happening for me at present.
I can live with it but hey if you want it to work as close to flawlessly as possible look at a 7xxx series card.