As far as screens, I have these 21in ViewSonic LEDs.
They are ok, the price was good when I got them and the size is good for my desk. But I did not get them all at once, so the color on one is a bit off.
My card has 2 DVI ports, and one DisplayPort. So 2 screens are connected to the 2 DVI ports. The third screen is connected with the dvi cable to the DVI/DP adapter, which is connected to the card's DP port.
Even though my cards are in Xfire all three screen have to be connected to the primary card, which is the top one in my case.
In your case it looks like you might need two DVI/mini-DP adapters since you have 2 mini-DP ports, unless you try to use the HDMI (though I am not sure if you can do that).