Thanks. I wasn't sure if the JPAC was way to go or not but given its Jamma that is likely the most reversible way to go?
Is the video output on the JPAC the way to go or do you recommend a 15khz capable video card?
To be clear, You need
both the JPAC
and the appropriate video card running 15khz by CRT-emudriver (or some other means).
Even after you get 15khz output from your video card, you will want video signal amplification for an arcade monitor. Why? Because arcade monitors expect stronger RGB signals than computer monitors and TVs, the signal strength will be relatively weak. You'll probably still get a picture on your arcade monitor without a video amp, but it will be faint.
The JPAC is a very popular choice as it plugs directly into JAMMA and acts as both a video amp AND a keyboard/controller interface between your PC and the arcade monitor. 98% of the time you will need both video amp and keyboard interface for MAME anyway. You can buy these components separately but this makes little sense as JPAC is designed for this purpose, is very simple to install and relatively cheap. In most cases you can just plug it in and it works.