Possum: Yes, when I plug the power supply into the Nomad I get a horrible machine-gunish noise in the backround (the power supply switching). And yeah, I know Nomads are crappy, but they were $150 cheaper than the PJB, and I wasn't an audiophile then.
Luckily 12vdc is the most common supply voltage so alot of possibility's are there. You could buy a good supply and stick it in a box, buy a kit and solder it up, or build from scratch. Have you considered which way you want to go?