Yes sad but true we here at Diamond have tried time and time again to see if there is a way with out a display port and no luck. If the card does not have a display port you can not use 3 monitors or eyefinity.
If it does have a display port you have to use a ACTIVE display port adapter or a Native display port (native means the monitor has a display port connection and use are using a display port cable with out any adapters)
of course an even cheaper alternative is to buy a second graphics card (the same as what you already have) and put them in cross fire as then you can run three or even 4 if you wanted to.
Buying another graphics card is not an option. I literally just purchased this one (and can no longer return it). In addition, I have neither the space nor power supply in my box to handle another card.