So just to get this straight:
A. (US) Turbografx-16 CD-Rom systems can play:
US CD games - off the bat (with corresponding system card)
Japanese CD games - some, but for others with hucard converters for the JP system cards to work on US systems
B. (JP) PC-Engine CD-Rom systems can play:
Japanese CD games - off the batt (with corresponding system cards)
US CD games - require Turbochip converters to work with system cards
** I own a Super CD-Rom2, which already comes with a System Card 3 firmware. So does this mean I can play virtuall every CD game out there (US & JAP), except arcade CDs?