I have been using AMD crossfire since the beginning of the year- 2 MSI 6970 Lightning cards.
Sadly, I cannot recommend Crossfire. In fact, I advise against it. I have removed the 2nd card due to DX errors and other lockups in games like BF3 and Skyrim. AMD might be a good choice for a single card, but From my experience I have to say that they don't have their act together when it comes to Crossfire. I now wish I had gone the NVIDIA route instead.
The newest NIDIA cards allow you to plug in and run up to 4 monitors, I think.
Mobo ASUS MAXIMUS IV EXTREME (REV 3.0)
Memory CORSAIR XMS3 8GB DDR3
GPU 2 EVGA 680 FTW 4GB
CPU Intel Core i7-2600K Sandy Bridge 3.4GHz (3.8GHz)
Drives 2 HITACHI Deskstar 3TB 2 Crucial 256 GB SSD Displays 3 HP ZR30w 30" monitors
UPS Cyberpower PP2200SW
PSU Antec High Current Pro HCP-1200 1200W
Case COOLER MASTER CM Storm Trooper
Drive LITE-ON Black 12X Blu-ray
CPU cooler Noctua 6 Dual Heatpipe
Fans COOLER MASTER SickleFlow 120
OS Windows 7 Premium