You need an active display portadapter to get the third, and for a fourth you'll need a second card.http://www.newegg.com/Product/Product.aspx?Item=N82E16814999031
I am interested in that site review, please post it. The 7770 is a good card, but its a middle of the pack card. Its not intended to be the top of the line and even those have trouble driving six displays by themselves.
Beware the internet, sometimes they lie. It says right in the HIS site, "AMD Eyefinity “2.0” technology enables you to expand your game across up to 3 displays. "