As far as I can gather, most people here recommend OCing slowly, testing in between steps and monitoring temps during the tests to find out what your setup will do comfortably.
There is no hard and fast rules except that everyone will get different results. There are too many factors, case, fans, setup, air flow etc to be able to say what you will be able to achieve.
IMO that CPU should be able to do about 2.65Ghz on stock cooling without too much problem if everything is setup ok.
As a suggestion, when you have to start increasing the CPU voltage the temps start to increase more so why not try to see how fast you can get it on stock voltage and test the temps then, I personally would not like to see my CPU temp go over approx 50C under load but I do intend to keep mine for a while.