|"Graphics Cards with 3 outputs, usually only allow 2 simultaneous connections.."|
That's why knowing the exact card is important. I took a shot at it in response 2 but the OP didn't comment. But if the card supports Eyefinity, it should support 3 indpendent displays.
"ATI Eyefinity multi-display technology
◦ Three independent display controllers
• Drive three displays simultaneously with independent resolutions, refresh rates, color controls, and video overlays
◦ Display grouping
• Combine multiple displays to behave like a single large display"