I used MSI Afterburner for both of my 560's.
Don't bother with memory OC until after you get your core closk where you want it. Stay below 1.050v for 24/7 use. And if temps get too high, try using the custom fan profile. It helps a lot.
I was able to get 960-ish with a single card, but when I went SLI, I had to add more voltage than I wanted, so I backed them down to 860 at stock voltage. (0.975v)