Nope, nope nope.
The extra 2GB wont help at all because the bus (256bit) is just too small, you may get 2.5 as opposed to 2, which will quite literally only help for a very select few games and it isn't worth the extra cash.
Also you can SLI the 2GB version perfectly well, if you aren't going to switch to a higher res any time soon I'd even recommend it.
And if you do have the money to SLI 2 of these guys in 4GB config, please god rather get a better (780, 290, 780ti) gpu in single-gpu configuration.
As far as performance, I love my 770, runs all those games at ultra quite easily. With ENB's and such on skyrim my FPS does sometimes dip to sub 40 (around 30-35ish), but it really depends on your mods.
BF4 plays phenomenally well, so does TW2 (installed it this week!)