It is possible to add a special 'eco' power strip to your arcade cabinet which will make it so that when you power off the PC or put it to sleep it will also turn off the other components (monitor, sound, etc). They have a Master outlet on them that senses when the power from a device (such as a PC) drops significantly, and when it does it turns off all of the daughter outlets. When the device/PC is woken up or turned back on it turns the daughter outlets back on. 

For an X-Arcade Cabinet, this means you can use the sleep button combination to put the PC to sleep which will then turn off the other components, and then press any button/joy to wake the PC which will in turn power the other components back on. At the Windows login screen just press button 3 (labeled Favs) on the player 1 side to log back in.

Examples of Power Strips with this eco function:

Examples of UPS with this eco function:

Power Options After Power Loss

You can press F2 as soon as you turn on the PC to go into the BIOS, and under 'Advance' change the 'AC Recovery' to 'Power On' or 'Last Power State' so that the PC turns back on if there is a power loss.