Thanks- I had bought the CNX-P2140 without realizing that it was only a dual 12V source, not an ATX source, so I then got an M4-ATX. I was planning to return the NIB CNX and run the M4-ATX, but now I'm pretty disappointing with the M4. (Emits noise that wipes out my factory radio FM stations, can't re-program it via USB, and their monitoring software REALLY sucks).
Instead of fixing the faults of the M4-ATX with feed-though RF filters, a shielded cage and a PIC programmer, I'm thinking of keeping the CNX-P2140 and buying a PicoPSU. As I said, it's an expensive way to go, but I'm a sucker for monitoring stuff and the CNX looks like it has a good monitor/control app.
I agree on the warnings though- I've seen threads about the Pico's already, and I haven't been around here long.