Using PSX ISOs on a Macintosh emulator

I have a Mac computer with System X Tiger, and have successfully used PCSX to play a commercial PAL game using the right BIOS image, but I tried doing the same with the ISOs that I downloaded from Romulation. Does anyone know what kind of BIOS image I should use or any other info that may help? Plus, even though the commercial CD of FF7 was working, it was very slow.