I am sry but dual agp gpus would not be good, First off do you not think they thought of Sli before pci-express, of corse they did, but dual pci-e split the 16x to 2 8x just like the agp only 2 not one, so if they did an agp dual, sli thingy, it would be 2 4x agp, the preforemance gain is 0.
anyway, I like agp 8x, and i dont hate you I am just stating the facts sry if i desroyed your dreams, of dual agp, nice concept, bad idea.