We're supposed to be trying to narrow down the bad parts, not adding more questions.

The PS is as new as everything else, from December. A big Thermaltake. Any suggestions on how I might isolate that?

I can run a single module at a time, but it will run single channel instead of dual channel. The mobo can also use either memory slot when using a single DIMM. I'll go unplug one right now. But I suppose to be thorough I've got to then later swap the DIMM to the other slot to see if it's a slot problem...