Well the max for the Q9550 recommended by Intel is 1.3625 but i would imagine you should be under that to hold stable somewhere around 1.33 to 1.35 should keep you stable but all CPUs react differently could be less could be more.
I have a q9550 at 3.4 (400x8.5) ghz and only 1.12 volts it runs perfectly stable. just try and see what you can do. use common sense. I strongly suggest not going above 1.2 I did and it got pretty hot but i was pushing 3.9ish ghz. never hit the 4.0 though (old mobo xfx 680i lt)
You can learn all kinds of neat things poking about the technical documentation.
badoosh, forget the RAM overclocking on a Core2 system.
I am unfamiliar with Asrock motherboards, but he is what you need to do ...
Download and run CPU-Z. It will monitor your RAM settings. You want a 1:1 FSB:RAM ratio.
Go back to stock settings, then adjust the RAM frequency to twice the FSB freq. FSB will be 333 MHz. RAM will be running at 667 MHz. Now start pushing FSB and core voltages up. You should easily reach 3.3 - 3.4 GHz. If you have an E0 stepping CPU, you should be able to reach 3.5 - 3.6 GHz.