In case anyone's interested, I rolled the dice on a 6GB r280x from MSI. It essentially is a single D700. Guess what, it works out of the box no flash or mod needed in Yosemite! No boot screen but that's not a biggie for me.
Getting about 52 seconds on BruceX test, and real time R3D half res good debater with blur node and noise reduction node apples on 4k Red clip! Not too shabby for under $300.
Anyone have a guess if the 295x2 will read as two discrete GPUs in a Mac Pro? That'd be better then dual D700's!