Directcu2 + reference card for Crossfire, good idea?

[f847]

For 7970 crossfire setup with a reference at the bottom and Asus directcu2 at the top, using ramapage iv extreme.

Both overclock to 1150 mhz (hopefully)

Do you think it is a good idea? or I am better off with 2 directcu2 ?

 

[f847]

Or dual sapphire vapor-x would be better?