techpowerup:Galaxy is working on a new GeForce GTX 680 graphics card. Pictures below reveal the Galaxy GTX 680 4 GB. As the name suggests, it is a non-reference design that's based on doubling the memory amount. The card features an out-of-the-box core OC of 1.10 GHz (base, boost not mentioned).
only way to do that is to buy something assembled already from futureship or some other store that will have to do
1600p monitors
3 or 6 screen gaming
Large screen TV's
are just some of the main reasons that you would need more Vram.
Most games operate just fine with 1GB of vram but occasionally you get the few that benefit from more vram although they run just fine with 1gb like GTAIV.
PC Games have more post processing, detail, and higher textures now a days than ever before so the extra vram is a welcomed plus to push things along.