i just mentioned you can play a PS3 ISO. obviously, PSX ISOs are possible only by three other ways:
multiMAN with cobra usb
jfw and their "experiments" with dynamic emulation
since i don't know much about jfw, i probably am saying this wrong so feel free to correct me.
also, i assumed we were talking about isos in general, so that means that we can, by only having a cfw ps3 with no dongle, get ISOs working, but only ps3 ones. and yeah, i ran Isos with that method once. Duke Nukem was the game i turned into an ISO and played.
hope i didn't lead anyone into a misunderstanding
"Whoever has ears, let them hear."