I've owned many incarnations of the PCE/Turbografx (PCE Coregrafx, SCDROM2 unit, Turbo Duo, PCE LT, etc.) and definitely recommend you get that over the Marty. Marty stuff, for one, is much more difficult to find (if you don't believe me, try looking for Splatterhouse for under $300, good luck) and you will pay much more in the long run if you decide to go for Marty over PCE. Plus, if I'm not mistaken, the CD drives on Marty's use a rubber band or something similar to get them to spin thus making them more prone to failing after awhile.
My suggestion is to either get a PC Engine Supergrafx or Coregrafx with the Super CDROM2 unit or, a PCE Duo R. Those are probably the most stable systems and will work practically forever if you take care of them. Too bad no one here mods them anymore for S-Video/region switch anymore, though. Man, I miss D-Lite....
Jon