Hey,
I have the same card and the best I could get rock solid stable pushing it to the limit is:
+700 memory
+100 clock
stock voltage
+120 power limit
All the performance comes from the memory overclock, it's 40fps out of the box for that alone. I tried higher clocks and even +120 gives random crashes in World of Warcraft. Also I did benchmarks and it's maxed out, going higher didn't give any gains. The fan curve is huge for these, I use 30% at 35c, then jump it to 40% all the way to 56c and take it in a diagonal up to 50% at 70c which covers any situation at 1440 mode pushing it to the limits. The other great thing that worked is mount a Thermaltake fan in the side case vent pointed right at the card so it's feeds outside air directly on to it. I mounted another one in the 3.5 inch empty bays with some foam to hold it and it's blowing across the whole card on both sides because the blank side of the card will hit 120f in certain spots, so a breeze helps there. Thermaltake comes with a 4 pin molex adapter and a low speed switch for 900rpm operation so it's super quiet and you don't need to mess with a fan curve for those.
To really see this card shine, go with MFAA supported games and put it to 2x MSAA and let MFAA effectively double it, omg everything looks great with that combo and with a framerate cap at 90 it's as good as a single card can provide. At 1440 mode the bad news is it has a lot more pixels to push, but the good news is it takes much less to make it gorgeous since it's got more pixels packed in the same real estate.