Preview release of a PC-Engine emu for the DC, heres what you needs ta know:
‘This can read two different kinds of files, *.pce and *.iso (where the iso is an image of the data track of a Super CD game.)

As far as I know, It supports all possible resolutions (not tested).

Roms should be put in the root of the CD with the emulator on it.

To play CD games you need to also have a matching System card rom that may be named any of the following things: syscard.pce”,”syscard3.pce”,”syscard30.pce”

Every game that I have tested runs about the same speed if not faster than in DreamEngine, but has sound.’
Get from this screamcast board topic & of course we have a topic on it as well here