After having ran this for a while I have noticed mixed performance. In most cases I can see clear performance gains with crossfire enabled. It seems though in rare cases performance may be worse.
Well 13.4 is stable, and did not let me enable it either. But yes I went back to 13.1. Just OpenCL isn't working so I can't fold. I (think) it was maybe working when I first set it all up before I updated drivers. But once I updated I know for sure it was not working when I go back. I know...
So, yes clearly I made a stupid mistake and bought non crossfire card to go with my crossfire card.
This is my original card is a SAPPHIRE Radeon HD 7770 GHz Edition Crossfire
The new Card MSI Radeon HD 7770 GHz non crossfire.
Now forgive some stupidity here as I haven't used crossfire...