can confirm, if the BIOS is 3.07 or newer, which all bare mainboards sold/distributed should be running, you only need the 60W adapter. It may not be a bad idea to get a 100W supply to check if you somehow got a board with the 3.06 BIOS. Otherwise, I would check the RAM to make sure that it isn’t causing problems with XMP, but I run 2666 sticks in my laptop and haven’t had any problems.
I will also say that it might help to contact support and see if they have any recommendations for a starting point or other precautions before using the board without a case.