Good job testing everything for a first time system builder!

to that!
Now onto other things to check.
Does the MSI board have onboard Audio? If so can you disable it during the installation? I would attempt disabling the onboard audio in the bios, along with the onboard NIC if possible.
It won't hurt to try it, even though I may be sounding absolutely crazy

I've seen very odd things in 15 years of system building.
If that still doesn't work then we can try some other things, you may indeed end up having a defective board, since the PSU should have nothing to do with a stop error of that sort, and you don't have any other pci cards in the system.