Well, I assume since it has a vga connection it is meant to just hook up to a computer. So you wouldn;t need an arcadevga.
However, if, for some reason, you wanted to run a game in mame at it's native 15Hz vertical frequency you need a video card that can output that. This monitor can handle that as an input so oyu need something that can output it.
The reason, I think, WG released this VGA based games iare getting common in the arcade. This monitor will allonw an operator to put either a game that uses standard resolution or VGA into a cabinet.