Since he wants to run Daphne, he'll need (OK, NEED is too strong a word, but life would be easy with) the ArcadeVGA. Other than that, I agree 110% with Grau.
JPac and ArcadeVGA are the way to go for you -- plug the ArcadeVGA into your computer, plug the JPac into your JAMMA harness, connect the ArcadeVGA to the JPac and you are off to the races (after misc stuff like driver installation, disconnecting power supply, etc.).
Cheers.