Easy there, my friend. In the first place, it's generally better to begin an overclock with FSB settings, then ease up the core voltage as necessary to improve stability. Increasing the voltage increases heat, so doing it unnecessarily is working against yourself.
You don't need a BIOS upgrade, at least not for this. Your FSB speed and ratio adjustments are on the board as jumpers. I learned this by reading the .pdf of your motherboard's manual on the ASUS website. I think that the next thing you need to do is read your motherboard manual. Very carefully. Sleep with it under your pillow at night. Seriously, the information you need about the mechanics of what you want to do is in there, but it needs to be looked at and learned.
By the way, the settings for your core voltage are, in fact, in the BIOS. Change whatever jumper you set for that back to default, or auto if that is an option. I would also look at the jumper settings on your slotket and have everything there set to auto until you can try your options from the motherboard.
Sorry for the long-winded lecture, but if you want to overclock, this is the way to go about it. Start with a good command of the mechanics of changing the settings for your particular hardware (read your mobo manual!), and then proceed SLOWLY. Really. Baby steps. Give your processor time to settle in at each increase, and you will be rewarded with a more stable system, and possibly a better overclock in the long run.
If anyone out there has specific experience with this processor and motherboard, jump on in.