will he sli double the memory ?!

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if your gaming at 1080p i'm gonna go on a limb and say yes.

Given that setup will currently game higher resolution than it is apparently being used for (you are using 1080p right?)

Unless some as yet unknown tech gets adopted quickly (which i doubt), as the market is driven by numbers (and to a lesser degree dollars therein those numbers) game developers will go where the numbers\dollars are. I used a 5870 for three years and was still able to play latest games until the time i upgraded. I still have the 5870 stored and i'm confident it would play even BF4 at much lower settings if i gave it a whirl. Having said that, 5 yrs in gaming is a very long time. In the next two years 2.5-4k gaming will become very affordable, regardless...
if your gaming at 1080p i'm gonna go on a limb and say yes.

Given that setup will currently game higher resolution than it is apparently being used for (you are using 1080p right?)

Unless some as yet unknown tech gets adopted quickly (which i doubt), as the market is driven by numbers (and to a lesser degree dollars therein those numbers) game developers will go where the numbers\dollars are. I used a 5870 for three years and was still able to play latest games until the time i upgraded. I still have the 5870 stored and i'm confident it would play even BF4 at much lower settings if i gave it a whirl. Having said that, 5 yrs in gaming is a very long time. In the next two years 2.5-4k gaming will become very affordable, regardless you should be able to get at least lower resolutions with 3gb vram and in sli 780ti the power to make usable frame rates. I could be wrong though, no one could answer this with absolute certainty.
 
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