I got my Q6600 up to 3.6 GHz in a GA-EP35-DS3P. Vcore was 1.42 volts. Load temps were 61 - 66 C, 24 hour Prime95 stable. All 4 of my Core2 systems are running at 1:1.
Unlink your memory settings. Run the memory at half speed. That will temporarily remove the memory from the equation and you can focus on the CPU. I'd do stopping points at 3.3 GHz and every 100 KHz after. At each step, stop and work on your memory settings.
Do not exceed 1.5 volts core voltage or 70 C load temps. Also do not exceed 1.65 volts on the RAM.
I thought that DDR2-800 RAM was rated between 1.8 - 2.1
As i recall mine was stock 1.9 and i bumped it to 2.0 so i could lower the timings to 4-4-4-12
It has been a while though