BTW, could I OC it to something like that with stock cooler?
Generally not recommended. They do not over engineer things so although there are great tolerances it is possible that with dust or even just warm climate you start to run into overheating problems.
you should know that overclocking causes increased wear so you should wait until you need the extra power.
There is nothing to wear in integrated circuits. Most failures are usually the result of dope diffusion from the semi-conductors so transistors fail. Basically the doping materials (placed inside the glass) are not permanently locked in place and over time they can move.
Overclocking with increased voltage level can cause them to diffuse more rapidly as it applies more force on the charges. If you were to over voltage an integrated circuit transistor sufficiently it will permanently break down almost instantly as the doping material will have diffused. This is how SSD memory (flash RAM) works in that it over voltages to cause permanent doping diffusion. It can undo the diffusion of the doping to some extent (when it clears) but this is imperfect which is why flash RAM only allows a limited number of write cycles.
Overclocking without raising the voltage will just produce more heat but it is raising the voltage that will shorten the component life. How much it shortens varies from component to component since minor imperfections might break faster.
It is worth noting that the power consumption increases linearly with clock. As sich raising from 3.0 GHz to 3.3 will be an increase in power consumption by 10%. It is important to know that power consumption is based on the square of the voltage. As such a small increase in operating voltage can significantly increase the power consumption. Practically all power consumed by the CPU is dissipated as heat inside the processor.
Do those extra 600MHz increase performacne significantly or it's barely detectable?
Single and multi threaded (up to core number) computationally intensive applications will see probably a 15-20% performance increase. Memory bandwidth intensive applications will see probably a 0-5% performance increase (as memory bandwidth is not increased at all). For games I would say anywhere from 5 to 15% improvement in CPU performance would be expectable since they can be memory bandwidth intensive. For CAD, modelling or video processing 15-20% would almost be a certainty.
Do not listen to people who say memory bandwidth does not matter. That was the case back in 1995 and even early 2000 but now it matters a load as memory bandwidth has not scaled as well as processing power.
