Overclocking a Gigabyte GA EP35 DS3R/DS3

I'm new on the board, I want to overclock on gigabyte which is mounted on Windows or Mac OS X. For my part, I'm on MAC because it is more stable and faster than its counterpart then the real iMac. I have used this system for long time which is now unstable, I prefer to change mac which is more beautiful than Linux. In short, I will want to O/C it.

First my config:
Gigabyte Ga ep35 DS3R
Intel Core2 Quad q6600@3.06Ghz
4 GB DDR2 Corsair Dominator 800
Maxtor 320 GB HDD SATA 1
PNY GeForce 7300 GS

1 / overclock at 3Ghz
So above all, set the BIOS: (Given to change) (it is possible to make changes so abruptly, perhaps the biggest surprise)

In "Advanced BIOS features"
Off the 3 functions:
- CPU Enhanced Halt / - CPU Thermal Monitor 2 / - CPU EIST Function

In "MIT" MB Intelligent Tweaker
- Robust Graphics Booster Auto / - CPU clock Ratio X9 / - CPU Frequency 3 GHZ (333x9)
- CPU Host clock control Active / - CPU host frequency 333 / - PCI Ex frequency 100
- CIA2 Deactive /- Performance Enhance Standard / - System memory multiplier 3.00 /- DRAM Timing Auto
- System voltage Manual / - DDR2 Overvolt +0.2V / - PCI-E Overvolt +0.2V / - FSB Overvolt +0.2V /MCH Overvolt +0.2V
- CPU voltage 1.3625V

In the case of adjustment "System voltage" after changing do not forget to return it to Auto.
Save and reboot @ 3.00 GHz.

2 / Overclocker@3.06 Ghz
Configure the BIOS in the same manner as above, with an update on the clock on 340 and the Vcore 1.36875V.
It is also possible with a Core2 Duo.

I will not hesitate to answer you on, more info on overclocking, but also on Mac OS 10.5 Leopard Xx86.

Hi Everyone,
To continue in overclocking.

3 Ghz Overclocking @ 3.10 Ghz
Configure the BIOS in the same manner as above, with an update on the clock 345.

4 Ghz Overclocking @ 3.16
Configure the BIOS in the same manner as above, with an update on the clock on 351 and the Vcore 1.375V.

5 Ghz Overclocking @ 3.40
Configure the BIOS in the same manner as above, with an update on the clock on 378 and the Vcore 1.41875V, but also multiple memory 2.5.

6 Ghz Overclocking @ 3.46
Configure the BIOS in the same manner as above, with an update on the clock on 384 and the Vcore 1.43125V, but also on PCI Ex Frequency 99 and multiple memory 2.5.

I followed this little guide to OC my Q6600 and my EP45-DS, but I did not increase the voltage. The latter is 1.325 v.
Is it dangerous not to do so?
I also plaque the multiplier of 2.4 to ram B to rotate at 800Mhz. It's GSKILL PC6400 PK.