Then don't run stress tests. Especially on the STOCK cooler. REMEMBER the stock cooler is minimal cooling, if you want better cooling and expandability for overclocking, you will buy a aftermarket cooler. The Cooler Master Hyper 212 EVO is a good choice.
Thanks for the advice
Probably i buy the Hyper 212 EVO in the future
However i've read many users having stock cooler with temps over 70ºC at max load (stress test i guess) and 35-37ºC idle which is quite less
What do you think? Could that be a reason to return it?