[Help] PC shuts down during AIDA64 full stress test (Chieftec VITA 750W PSU, Ryzen 5 7600 + RTX 4060 Ti)

Hey everyone,

I'm having an issue with my new build and could use some advice.

My Specs

Deepcool Case | MATREXX 55 V4 C

AMD Processor | Ryzen 5 | 7600

Gigabyte b650m d3hp | Processor Socket Socket AM5

Kingston | 16 GB | Memory module

DDR5 5200 MHz

Lexar NQ710 1 TB PCle 4.0 x4 (NVMe)

MSI | GeForce RTX 4060 Ti VENTUS 2X BLACK 8G

Chieftec VITA 750w

The Problem

When I run AIDA64 stress test with everything enabled (CPU, FPU, cache, RAM, GPU, local disks), my PC shuts down instantly after a short while.

If I stress CPU only, GPU only, or even CPU + RAM + disks separately, it runs fine.

The shutdown only happens when everything is stressed together.

Event Viewer just shows Kernel-Power 41 (unexpected shutdown). No BSOD.

What I've Tried

Lowered GPU power limit in MSI Afterburner to 87% and set 80 °C temp limit.

In BIOS, experimented with PBO Enhancement:

Tried 70 Level 1 (closest to Eco Mode, ~65 W CPU power).

Also tried 80 Level 5 for a balance between performance and efficiency.

Temps are fine (CPU <85 °C, GPU <80 °C).

System is stable in games for a few hours, then randomly shuts down (ram rgb stays on)

Still, AIDA64 full stress causes shutdowns. I have other PC that works fine even for hours, this new one shuts down after 3-6mins

My Question

Is this definitely my PSU (Chieftec VITA 750W) being too weak/unstable under combined load, even though wattage is "enough"?

Or could it be motherboard VRMs not handling full CPU+GPU stress?

Would replacing the PSU with a higher-quality 650-750 W Gold unit (Corsair RMx, Seasonic Focus, be quiet! Pure Power, etc.) likely solve this?