I don't have the exact video cards your recommending but i used 2x 8800GTS and i can tell you my Q6600 went nuts when I took the cards out of SLI (I didnt enable SLI) and put a second monitor on the second video card. I 5 box and my CPU usage for them was around 40-50% per core. I ran at 80-90% after splitting the cards with separate monitors.

Now im setting up a second computer moving one of my GPU's to it.

Anyone want to buy a wife so I can upgrade???? Cheap and EZ man, Cheap and EZ......