What operating system are you running? I doubt you will need a BIOS update, more than anything you might have to enable some settings in the BIOS by the looks of the manual
However i know that you can enable Hybrid CrossFireX with these type of boards:
"C. BIOS Setup
Enter BIOS Setup to set the following items under the Advanced BIOS Features menu:
Set Internal Graphics Mode to UMA. (Note 3)
Set UMA Frame Buffer Size to 256MB or 512MB. (Note 3)
Set Surround View to Disabled.
Set Init Display First to OnChipVGA."
(Now regardless of wether you plan on using CFX or not, i'm sure you should be able to use the built in video for a third monitor).
I can also tell you that:
The DVI-D port does not support D-Sub connection by adapter.
Simultaneous output for DVI-D and HDMI is not supported, but 15-pin VGA + DVI-D is.
Hopes this helps some =)