your cpu is what you need to have a conceren for. probably what you need to overclock to is 750/1500/1000. the shutoff point is 100. I like to keep it in 80s if possible but probably not gonna happen with most modern games. i have an alarm that sounds through real temp if the cpu tem reaches 96. i would recommend that and save, quit, and then turn the turbo boost off in the bios.
As long as your temp is between 60C ~ 85C, you are good, my OC is 600/1200/900 (Core/Shader/Mem) at idle, 800/1600/1100 (Core/Shader/Mem) at full load. And the average temp is 65C ~ 75C. Oh and I use a cooler so if you dont have any cooler, I do not recommend to OC it too high.
The GTX580M is only close to on par with a GTX 560 Ti, so no the 555M will not reach GTX 560 performance, but we could easily hit GTX 560M performance with volt mods and overclocking. People say the 560M is close to the GTS 450