Originally I read these two "Notes" in the paper manual and the e-manual for this motherboard. English manual from Asus download page.
On pages 45 and 46 I found these 2 seemingly contradictory advisory notes;
1. We recommend that you install a VGA card to the primary (blue) PCI Express slots, and install any other PCI device on the PCI Express slot (black).
2. In single card mode, use either the blue or black slot for PCI Express x16 graphics cards to get better performance.
So, can I put a single BFG GTX 260 and run it from the black or second PCI Express x16 slot?