Well here are a few suggestions.
Try some more voltage while you are overclocking just to see if you can get stable at all. You can always work your way back down later. From what I've read it sounds like you could go up to 1.4V safely, but I'd say 1.35V max just to play around.
That said, what you should do first is figure out how high you can move the FSB. So what you'll want to do is actually underclock the CPU first by moving the multiplier to it's lowest setting. Guessing that's like 5x or somewhere around there. Then at stock fsb your speed will be around 1667mhz and well below what your cpu can do. Then slowly raise up the FSB until you reach a point where that is no longer stable, and back off a little bit. Guessing you should be able to reach 1600mhz - 1800mhz FSB stable. (400 - 450 in bios) Might need to just try making jumps while doing that as sometimes there are ranges that just won't boot, like around 1450 - 1500mhz fsb. At 1600fsb the cpu is only 2.0ghz using a 5x multiplier. Then when you move the mulitpler back up to 7.5 you would be at 3.0ghz.
Once you find the highest fsb then that gives you an idea of how high you can do with the cpu. Just start bringing the multiplier up 1/2 step at a time and keep testing. I'll add more later but I have to run.
Make sure that your ram isn't being overclocked while you are doing your testing. If anything you want it to be underclocked so you know that ram isn't causing the issue.
Here is a link to someone else's numbers with your board. http://www.overclock.net/intel-mothe...50i-guide.html
Didn't realize you have a 750i chipset, but you might have trouble getting the FSB that high. I simply canot get my 780i over 1520mhz FSB and keep it stable. Think it's all going to come down to if you can get a stable FSB at 1600mhz.
Guessing the HT and NB voltages both might need to go up a hair to reach your target.