RGB can come from the PC Engine. That is how my system is setup. However, you will need to pull audio from the interface unit. With a CoreGrafx, you get mono audio returning from the IFU to the system and out of the DIN jack on the CoreGrafx, but you have to grab audio from the IFU if you want stereo. I do not know if the PC Engine is wired to get any audio back from the IFU as I do not have one to test with, though.