GTX670 4GB is alot Better than 7950 3GB.
If you can Get it. With 4GB VRAM its a Very Awesome card.
If you can wait, then wait for the Next-Gen Cards.
In 1440p you need alot of VRAM, you'll easily Cross 2GB in Most Demanding Games.
And Skyrim + Texture Packs is Ultimate VRAM Killer
The Benchmark is of 1600p, So just add a few fps and you'll get the Same.