I don't know how well video cards handle multi-head / multi-monitors in Linux but it seems a lot of issues come up and support isn't great?
But, on the Nvidia side, the link above seems like the best choice for now. Not sure when that card will be released unless it is already.
That's all I have to suggest. There are ATI owners who are trying multi-head setups but they are better sources to give you feedback.
Also, I am not sure if the Display Port connections work well (for multi-monitors) but that's another subject.