Thanks guys
The problem for me is... temperature!! As others have correctly stated 8GB puts more stress and strain on the NB.
At Stock Clocks my NB reaches a staggering 51C during Linx (20 runs of "6896MB") and up to 54C according to the LCD Poster during heavy gaming. (Yes a Single PCB GTX 295 can make the NB rather hot when it is working hard).
When I raise to 1600FSB the NB reaches 59C during heavy gaming of 1hour and 52C during Linx.

I think 8GB + Quad Core really does hamper what you can achieve with clocks...therefore I am not going for anything Xtreme, just something which increases my performance mildly.

Leeghoofd you are a dab hand with a QX9650?
What Voltage would you suggest for the Vcore (on Air with a Xigmatek Heatpipe cooler)? I am aiming to keep bellow 1.3265V Vcore and 1.58V on the CPU PLL. Ideally I would like to acheive 3.4Ghz with 1600FSB, however I may have to sacrifice on the RAM clocks here.
Interestingly I have noticed that raising the multiplier requires a BUMP in NB volts (not CPU volts). Is this because >3Ghz Quad Core is more taxing on the NB?
Perhaps I am being too ambitious, but I am certain Intel did make a Xeon based 45nm "Core" series CPU which ran @ 3.4Ghz 1600FSB so in theory I could aim for this :p

Zeus
How hot did your NB run on air? and how much did moving to water cool things down?

Thanks again
John