KeyPower

KeyPower makes ATX-compatible DC-DC PSUs that are primarily for industrial use. They lack many of the features of the other products listed (start-up/shutdown controller, battery protection, etc.), and are not designed to be as efficient as comparable products. Until recently, they were the only manufacturer to offer a 250w DC-DC PSU. Their current product line includes DC-DC PSUs rated as high as 350w, but are not available at their online store as of this writing. The KeyPower units are the same size as a standard ATX power supply (150mm x 86mm x 142mm / 5-7/8" x 3-3/8" x 5-1/2").

Keypower KP-DX250H
12v rail = 10A (120w)
3.3v rail = 14A (46.2w)
5v rail = 25A (125w)