As long as you do not Crossfire the cards it should be as simple as connecting two monitors to one of the cards, and one monitor to the other card.
This will not work.
You need to run all monitors off one card with one connected via an ACTIVE display-port to DVI adapter. Connections otherwise do not matter whether you go with DVI/DVI/DP(ACTIVE) or DVI/DP/DP(ACTIVE) or HDMI/DP/DP(ACTIVE) etc. So long as one is connected via an active adaptor to provide a third clock signal it will work. Also contrary to what you may read in some places it DOES NOT have to be a powered adaptor (though this can depend on what resolutions you plan to run). See http://support.amd.com/us/eyefinity/Pages/eyefinity-dongles.aspx
for eyefinity validated adaptors.