Should there be much difference between sli 660ti and a 980? My 7950 xfire performs about hte same as a 980, maybe slightly less powerfull, but if i remember correctly a 660ti was only slightly below a 7950, maybe 10% or so.
Maybe you need to move to a higher resolution to notice a big difference to make use of the extra vram.
Maybe you need to move to a higher resolution to notice a big difference to make use of the extra vram.