Eyefinity is using 3+ monitor as a single one.
Dual display's have nothing to do with eyefinity.
Wrong. Eyefinity creates a single 2048x768 2x1 vs. extended desktop with two 1024x768 desktops "extended" or 1+2
I am currently using dual projectors, and let me warn you, it's a pain. I can't tell yet if it is the cables or the cards but one has a blueish hue on the left regardless of which projector I put there, so the middle is becoming impossible to match with colors. I am going to troubleshoot my cables, but I think it's the cards, they suck with vga over adapters. Maybe two or three digital projectors, but you are talking some serious dough.