Just in case nobody posted this yet regarding the random restarts/hangs due to the spikes

 I'm using AcBel R88 1100w and it's already 4 years old. I've been using it since the litecoin mining days of my 7950s and r9 290s.

Here are the things I did:
1. Distributed the load across the 12v rails. (If your gpu needs 2 PCIe Power connectors 8pin or 6pin.)
2. Added capacitors in the 12v PCIe power near the GPU. (I placed 3300uf 16v capacitors on the pcie cables near the PCIe connectors. I didn't need to splice the cable, I just tucked it in the back of the pcie cable making sure that it reaches the 12v(yellow) and negative wires(black).)
3. Clean the PSUs to reduce the temps to avoid triggering thermal protection.

If it stops the random restarts, good for you. It means that your PSU could actually handle the load. If it doesn't, then your PSU probably has other components that are at fault.

After doing these, I was able to eliminate the random restarts and it also allowed me to OC my GPUs again without problems.

YMMV.