I am curious, why the 4GB? I have pure data supporting these common questions;
When games require over 4GB Vram, it'll help; False.
Greater Resolutions will benefit from the 4GB Model; False
The 4GB Model will be able to last longer in the future (games); Also False
SLI 4GB will help; True.
The 4GB Models can utilize up to 3.8GB of the 4GB Vram, but when it does use it, the core itself is struggling, adding no benefit to the cards performance. In Crossfire, if you have dual 2GB Cards, it does not mean 4GB Vram, only 2GB as the world of Crossfire (and SLI) means; 2+2=2, 4+2=2 and 4+4=4. With Vram the 4GB will only help In crossfire, nothing else.
If you have other questions regarding Vram, just ask and we'll gladly help.
If you want reviews supporting this, am also glad to find them.