ThrottleStop will let you change your multiplier higher than the default multiplier and it "might" let you adjust the voltage going to your CPU. If you have this motherboard you can download and play around with ThrottleStop right now to test this out. Run Prime95 Small FFTs on your present CPU until the core temperature has stabilized. Start ThrottleStop, adjust the VID to the maximum and then adjust the multiplier to the maximum.
These maximum FID and VID values are simply the maximums for your CPU. The non-Extreme CPUs are locked by Intel so you don't have to worry that the maximum VID voltage is going to hurt anything. That's just the default for your CPU.
After that, put a check mark in the Set Multiplier box and then click on the Turn On button. While fully loaded, lower the VID setting one notch at a time and see if it has any effect on your CPU core temperature. If the temperature changes at full load based on your VID setting then the voltage going to the core is changing. If your computer crashes when playing with the VID at full load then that means you adjusted the VID voltage too low for your CPU.
Are you 100% certain that your motherboard bios supports a QX6700 CPU? Sure it will physically fit in the socket on your motherboard but if the bios doesn't recognize it, your computer might not boot up. It will sit there with a black screen staring at you and the CPU fan will spin and that's about it.
You can adjust the multiplier of a QX6700 or QX6800 with ThrottleStop so if you are going to experiment with this, you might as well buy the cheaper QX6700. These sell for about $80 on Ebay.
As a hobby, I enjoy spending a small amount of money to try and make some old computer run much better but I would agree with others that you are probably better off just selling what you have for whatever you can get for it and moving on to some new hardware. An overclocked QX6700 will be like a small nuclear reactor. Better make sure you include a decent heatsink in your budget to keep it cool. Edited by unclewebb - 1/27/13 at 9:15am