I dont plan to overclock the GPU's too much, not enough to cause a drastic difference at least. and yes I run Skyrim heavily modded. Plus I bought the 4GB card about 8 months ago and I would like to add to rather than sell and buy new card(s). I like my 680 quite a bit so I dont want to replace it. If they (ASUS) hadn't discontinued this card I would have gotten another one now. On Ebay they have the 4GB model but last I checked they were selling for $1500+.
Edit: They're $1750 now... http://www.ebay.com/itm/New-Asus-NVIDIA-GeForce-GTX-680-4GB-GDDR5-2DVI-HDMI-DisplayPort-pci-e-Video-/171015585057?pt=PCC_Video_TV_Cards&hash=item27d152bd21