Personally, I would say that my setup is "fine" when I'm running BF3 and Crysis II DX11 maxed out 7680x1440, 4xMsAA and 16xAF with Vsync and my FPS never drops below 60.Got some benches with multiple VRAM sizes? "Fine" is a very broad term.
I don't have any benches since I've never seen any benches at this res, but keep in mind that 1440p is 1.78 times more pixels than 1080p.