I have two R9 290x & a 3930k installed on an Asrock X79 Extreme9. The system is connected to 3x 30" monitors - two Dell 3011s and one Dell 3007. The system is powered by an 1100W Silverstone PSU.
When I enable crossfire, I get the same BSODs that you mention. It will also sometimes just freeze completely without a BSOD, requiring a hard reset. I am running the latest drivers that were released on Dec. 18th.
I do not believe it is a power or heat issue, because I do not need to be playing a game for the system to freeze. It can happen just idling at the desktop with nothing running. The system is completely stable with crossfire disabled.
I have read that there may be a compatibility problem with the R9 cards and crossfire on X58 & X79 boards.
Apparently there was also a similar issue with some of the 7000 series cards that it took about a year to get fixed.