I have not looked at any new specs/designs out, but when I built mine two processor mainboards are mainly for servers. They have to run server processors (Xeons or similar) and are more setup for different processes than video/memory that is required from a gaming rig.
Things might have changed since then, but a quick google search and I could not find a good reason to run the added expense over a single 8 core. I run a AMD vishera 8350 (4ghz) which I bought when they first came out, was labeled "worlds first 8 core desktop processor" and its a monster even though its a year old now, I have never slowed it down with anything. Looking on new egg there are tons of 8 cores now, even faster for less than what mine was.
Just might be less of a headache/hassle.
And I wanted a titan, they had just came out when I built mine but it was the price of everything else I had together lol. They are good chunk cheaper now but still kinda pricey.
PS about the video card, many support multiple monitors on one card. Mine has 4 outputs, I run dual monitors hdmi from it.