Upgrade to better GPU or to SSD?

[Les]

Originally Posted by bw_wolverine

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I enjoy playing ArmA II pretty much weekly with friends and I think I'll stand to benefit a great deal from the GTX 580 ...

For what it's worth I recently went from a GTX285 to a GTX580 and it gave me something like a 20fps (don't quote me on that or get your hopes up) boost in ARMA2, basically making an unplayable game, playable. Of course I then went and upped the settings to make it unplayable again, but now have it in a playable, better-than-it's-ever-looked state. Which means I can finally see exactly how those diabolical AI are killing me, well, sometimes anyway, sneaky buggers.