ArcadeVGA card from ultimarc:
http://www.ultimarc.com/avgainf.htmlI don't own one, but it is pretty much standard equipment for most BYOACers wanting to display thier PC through and arcade monitor.
Please note that you will need a PC with an AGP slot for the video card. Make sure you read and undestand all instructions on ultimarc's website pertaining to monitors and ArcadeVGA card so that you know what else you need (eg. VGA breakout cable, video amp, etc.)
WARNING:
PLAYING WITH A MONITOR CAN BE DANGEROUS IF YOU DO NOT KNOW WHAT YOU ARE DOING. THERE CAN BE 25,000 VOLTS OR MORE STORED INSIDE A MONITOR, EVEN IF IT HAS BEEN UNPLUGGED FOR A WHILE.
Ultimarc has a pretty good monitor FAQ. Please read.
If you have a working arcade monitor, then that is the best way to go. It will give you the best, most authentic picture quality for all those classic games.
If you do not want to mess with all of that, you can take out the monitor, and put a PC monitor or a TV in there instead.
I bought a Williams High Impact arcade machine at an auction, but the monitor did not work, so I took out the 25" arcade monitor, boxed it up and stored it untill I have enough money to get it repaired. In the meantime, I put a 27" TV in the cabinet and I am quite happy with the results. I am using a TV with RGB component inputs and it works way better than S-Video or composite.
Hope this helps. If you decide to go with the ArcadeVGA, read the threads about it to see how easy or difficult it would be to setup.