Erm, yeah, the cards support it, but your CPU and motherboard will croak.
Why do you even WANT quad-sli anyways? The benefits over two cards aren't amazing.
Keep in mind, running four cards does NOT mean you have four times the rendering power - only that you've spent four times the money.
I guarantee you that, as much as I love the 670, whatever your task is, there's a better option.