The difference you're seeing between your BIOS and CPUZ is what is called vdroop, it happens to everyone and is normal. Go off of what CPUZ is saying that your current voltage is at. AI Suite is for the most part trash, don't mind it at all. It also sounds like you did the automatic overclock option, I STRONGLY STRONGLY suggest not doing that option and spending a little more time researching on how to overclock properly, you're in luck because Sandy Bridge is VERY easy.
Also, just to make sure you know what the peak voltage is for your CPU, try running Prime 95 and CPU-Z at the same time. Your CPU will use more voltage when running at 100 percent, so go off of that number and make adjustments as needed.
vdroop, I hate this thing. What I can suggest is finding the options for the droop in your BIOS and put it on medium or disable it if possible (that is, if you don't want to deal with it like I did not)
Basically, what it does is change the voltage of your CPU from the set value by some amount depending on load. If you want to keep it as-is, know what is the max voltage your CPU goes to and consider that while you tweak your voltage. Basically, do as Vortex88 mentioned; Prime95 and CPU-Z. The data sheet for this processor says that the max voltage should be 1.52V (it's under VID so I think it's the right one) and therefore you should try and not exceed that one whatsoever, at least not for long periods of time.
Also, I need to echo B-rock in saying that you might want to tune things manually. Automated tools tend to be very conservative in pushing the hardware.