I have the exact same computer in my MAME machine. It works great. There were plenty of electrical connectors, but if I may offer a suggestion, why don't you just go buy a used power supply for about 5 bucks, plug it in separately and just tap into it?
I have everything running through a smartstrip, an dthe smartstrip is triggered by the computer. It was also easy to tap into the wires for the PC's power switch so I could mount my own switch on top of the machine.