Yep you kinda got it right. I would check out FurMark as a temp stability program http://www.ozone3d.net/benchmarks/fur/
Or you could just run a GPU intensive game, i stability tested my 5770 with GTA IV. But just OC slowly and take your time, the last thing you want to do (even thought it might seem tempting) is jam those sliders to the right and fire up a game. And i would make sure your GPU temps don't go above 85C at load, above that and you will probably start to see artifacts on your screen in games. Also how do you like your X3 740? I am planning on getting one soon. The biggest jump you want to make is probably 20hz after that go slowly on both the core and memory.