Assalamoalikum bro,
I saw your message, bro first see what is the stepping of your processor. I mean either its a E0 stepping or C1 stepping. Use CPU-Z to check that, E0 stepping quad is easier to OC while C1 gives hard time to OC. Mine is C1 and it cause some trouble before getting stable. I think your's is also a C1 stepping quad as its giving you trouble. But yes I managed to crank it upto 3.4 GHz lately and its running fine so far.
1, Bus speed is 400 MHz (for 3.4 GHz)
2, System Memory Multiplier is 2.0 (for my XMS2 800 MHz DDR-2)
3, Vcore is 1.3000v to make the thing stable.
Gigabyte boards are quiet good in terms of overclocking, before this quad I was using a E6550 C2D and easily overclocked it from 2.33 GHz to 3.00 GHz and now this Q9550 is at 3.4 GHz which is pretty good. So you can go for a Gigabyte board.
Feel free to ask anything you like
Take care.