They have a lot of things wrong with this article about setup:
In a typical 3x1 configuration, two displays could use a DVI port and the last could use either HDMI or DisplayPort, whichever you have available.
Note that if you are planning to take the 3x2 route, Eyefinity 6 cards demand a $100 premium over regular HD 5870's. The price is justified, though, as that price includes all of the dongles that are required, along with the fact that Eyefinity 6 cards come equipped with 2GB of GDDR5. If you are planning to go with a CrossFireX setup, two regular HD 5870's will be suitable as well. You will just need to have the proper dongles/adapters handy. ¹
I Will say they did correct this at the bottom:
¹ This has proven incorrect. AMD has stated that in CrossFireX mode, the ports on the secondary graphics card are disabled, therefore you are limited to the ports the primary card offers. You can still use six displays off of two graphics cards, but CrossFireX will be disabled. It's one or the other.