More than likely you have maxed out the power VRM on your board and no about of volts will improve your overclock. At stock your cpu is a 95w and should be thankful to have gotten to 3ghz. Beyond that you can try lapping the cpu ihs and going WC.
Next stop should be a guide for your particular motherboard. Google is your friend.
Go through the guides. Then take your core voltage off Auto and set your memory voltage to factory recommended values. Change the System Memory Multiplier (or whatever your BIOS calls it) from AUTO to 2.00, 2.00B, or 2.00D - whichever you need to set the Memory Frequency to twice the FSB. Then when you increase the FSB, the memory clock will rise in in proportion with it. At an FSB of 266 MHz, your memory clock should be at 533 MHz.
Download CPU-Z to check your FSB:RAM ratio. It should be a 1:1 ratio.
Pay attention to your memory settings. I bet you have them on Auto and that is limiting your overclock. At 3.2 GHz and a X9 multiplier, your FSB freq is about 355 KHz. With memory settings on Auto and DDR2-800 RAM, your memory is running at (355/266)*800 or about DDR2-1066 speed. Asus uses "straps" for memory speed adjustments. You need to find a setting, that at stock freqs, gives you an FSB:RAM ratio of 1:1.
Then start the cycle of increasing FSB and CPU voltage. What's your VID? Around 1.25 volts is sort of average. Anything over 1.3 volts will limit your overclocking.
Don't exceed 1.5 volts vcore and 70 C. 65 C would be better.
I have a G0 Q6600 in a Gigabyte GA-EP45-UD3L with a Xig Dark Knight running at 3.6 GHz in an Antec 900 case. Vcore is 1.425 volts. Core temps are 61 - 66 C. System is 24 hour Prime95 stable.
Thing to keep in mind is that all CPU's are different. Most of us are getting 3.3 GHz to 3.6 GHz with around 3.4 GHz the average.