Yes but flashing your bios is something that is hard to do remotely without ipmi/lilo, and not very efficient when you're trying to find the voltage floor for a card.  Once you've found it, by all means create a modified bios (unless you're on a 290/290X... in which case this would be a nice non-signature breaking way to do it).

The other thing to consider is you can also READ the vrm voltage off the vrm itself.  This gives you exact voltage down to the millivolt in some cases.  You can also read amperage on most of these vrms.. this gives you true wattage.  This is valuable information for system tuning/sizing.