What you really need to find out with your combination of board and CPU is to determine your max stable FSB. Once you've figured that out, you'll have a solid point of reference. Since you have a 680i chipset, you can unlink the memory from the FSB clock, making this a whole lot easier.
The 680i is easily capable of obtaining FSB speeds of 1600MHz and higher, but it's the combination with your particular CPU that determines your actual FSB roof.
To start off, set your memory unlinked to 1066MHz, timings 5-5-5-15 2T. That will guarantee your memory will not be the limiting factor in your FSB search.
Then start out by setting the FSB to 1350MHz. Set the multi for the CPU that it is as close to stock speed as possible without going over stock speed (2.4GHz). You'll have to adjust the multi down every time the speed goes over 2.4GHz while you up your FSB. You'll need to set the voltage on your CPU to stock volts (1.21v), as well as the NB to stock speeds (1.3V). The FSB volts need to be at stock too (1.2v)
Now, starting from 1350 MHz work towards 1600 in 25MHz increments. (Don't forget to push back the multi to stay at or under stock speed). Once you begin to notice instability, up the CPU voltage by 50mV, relatively big jump. Once you start upping the voltage, keep both the NB and FSB voltages as close to the Vcore as possible. +- 75mv (this yiels the most stability because of how the FSB AGTL+ electrical characteristics work). Once you get the CPU stable, continue upping the FSB in 25MHz increments. Repeat this untill the amount of volts you need to add just becomes too big relative to FSB gain. This pivot point will be somewhere at 1.4V Vcore. From then on, you'll need much more volts to get a decent FSB increase.
When things are right, you should be able to hit somewhere between 1600 / 1700MHz FSB. Once you need to apply more than 1.45V some, stop there and set volts back to 1.4V. (down 50mV) Now step down the FSB in 10Mhz increments untill the CPU is stable with 1.4V core (In Bios, under load this may be 1.35v).
Now you found the FSB sweet spot for your CPU while still leaving voltage headroom for the multi increase.
I can't remember if you can adjust the VGTLREF lane voltages on that board, but if you can, leave these to auto. Generally the BIOS is smart enough to adjust them properly for you.
Now you can just up your multi and add Vcore accordingly to reasonable levels. (1.5V in bios max, if your cooling allows). I would recommend to stay below 1.5V though, to maintain FSB stability (remember to keep FSB / NB volts as close to Vcore volts as possible for optimal FSB stability).
Once you got the CPU prime stable, you now can adjust your memory speeds. Synced at 1:2 would be a good idea. Say you managed to get up to 1650FSB, set the memory speed to 825MHz. This allows you to tighten memory timings quite a bit. The effective speed of the memory remains the same as if you were to run 1066 with more lose timings.
Well.. hopefully that gets you going into the right direction
The most important thing to figure out with your CPU is to find the turn-over point at which FSB speed you need to start increasing voltage while keeping effective clockspeed at or below stock.