throwing this out there, but one of the biggest basic issues i see with people attempting an eyefinity setup is that they don't understand that one of the monitors needs to be a DisplayPort monitor and connection, Example: DVI+DVI+HDMI won't work, but DP+VGA+DVI will or DVI+DVI+DP will, or DP+HDMI+DVI will.
TL;DR You need one of the three connections as displayport.
For eyefinity, the 3rd monitor must be connected via displayport in order to achieve the higher resolutions enabled in eyefinity. If your monitor does not support displayport then it must be connected via an ACTIVE adaptor, not passive. The following link has a list of approved dongles.