Well, the up-to-date kernel is still overheating... :(
On CentOS6, with the same running environment (XFCE + firefox), I get this:
Core 0: +56.0°C (high = +86.0°C, crit = +100.0°C)
Core 1: +57.0°C (high = +86.0°C, crit = +100.0°C)
This is 30°C lower. So I tried to disable...