I want to touch on the subject of ATX PSUs for powering the arcade stuff in case you wonder why I opt for the arcade dedicated PSUs instead.
ATX PSUs typically have high power rating, like 250-500W, that's what most people will use, because they have a spare one after upgrading their PC, or just find one cheap. Problem is, arcade PCBs don't require that much juice, you'd be hard pressed to find a game that needs more than 50W (perhaps games from early-mid 80ies), most will require 10-30W, which is like nothing for the ATX PSU. A short circuit that has some small resistance (i.e, +5V/+12V isn't shorted directly to GND) won't trip the PSU's short circuit protection immediately. Such short will basically be seen as load, so the PSU will push more amps before it detects the short (especially a cheap ATX PSU). A 250W or more can push a lot of amps, in result it can fry the PCB, or even melt the wires (depending on their insulation rating).