I've owned a PC Engine Duo-R for a very long time now and have never had any issues with it... It plays every Hu-Card and CD-ROM² game ever released. The only exceptions are the five SuperGrafx, the twelve Arcade Card exclusive ones and Jūōki (A.K.A. Altered Beast) that, for some reason, is only compatible with the System Card 1.0.
They seem to be going up in price recently, but if you are patient enough, you may end up finding one for the equivalent to US$150,00 on Yahoo! Auctions (in Japanese).
https://bit.ly/2EiAhPcYou may need an adaptor to play US Hu-Card (or Turbo Chip) games, but since I always hear about how hard it is to find Western TurboGrafx-16 games and how much cheaper they are here in Japan, I'd say the Duo-R is the way to go!
(No need to invest on a Duo-RX though. The only major differences between it and the Duo-R are the color of the CD tray's "open" button and the joystick that comes with it, which has 6 buttons... Just go for the Duo-R)