I'm doing (another) Prime95 test as we speak, at 100% load here are my max temperatures:
Core 0: 51 °C
Core 1: 51 °C
Core 2: 55 °C
Core 3: 46 °C
As you can see, 9 °C difference between hottest and coolest core. I'm still unsure if I should reseat the heatsink or leave it like that. Supposedly it's nothing to be alarmed about.