Necessary BIOS Files...rly necessary?

Hey,

i just wanted to ask if all the BIOS files are rly needed, i mean:
rom1.bin, rom2.bin, erom.bin, scph-xxxxx.bin, scph-xxxx.nvm

I got the schp and rom1, the nvm one is created when you configure the BIOS, setting the time, calendar and such, so i got it too. And rom2.bin as in the guide says its a kinda only for Chinese PS2s, so not really needed.

So i want to know if i am good to go, or i need that rom2.bin file and/or the erom.bin?

Cheers.