Yeah, if you want to future proof it, I would actually wait a bit till the 700 series is out. bf4 and the 700s should be out around the same time.
As for video ram, I would say 2gb should be a fine card unless you have plans to run triple displays.
I have a gtx650ti 1gb card in mine (stock was the 555) I run triple screens on bf3, the card can handle it on medium, but if I go up to high settings, then I get booted by punkbuster since my system cant keep up.