I have had very good luck with an Antec Basiq VP350 ATX power supply.
I paid $30 Canadian for it. It advertises two 18amp 12v rails.
While I had it running my J-Head mk iv hotend and PCB heated bed off one 12v rail (Molex), I cut off one of the four-pin 12v connectors and crimped on another 4-pin molex to run my bedplate and make use of the second rail.
