@RippleCarry: Yeah, 500W should be more than enough. Since you have the latest chipset drivers, can you check if changing the Windows Power Plan affects the boost?
Cooling shouldn't affect the boost, unless you actually hit >80 degrees when boosting, which doesn't seem to be the case, as the CPU doesnt boost high or for long. My only concern (barring an actual hardware issue) is that the VRMs become hot and restrict the CPU from boosting, but the Mobo is a good one, and I have never seen above 50-55 C on them.
Lastly, have you also installed MSIs Dragon Center app (os something like that). It's like their Afterburner app, but for CPUs. See if you can affect the power delivery and boost clocks through it.