So I tried the E6700 at 9x and 8x to see what happened.
The only Bios setting that helped at all was to set the ram to SPD - no voltage changes let me go higher than 379FSB. With SPD on i could do 410FSB before it would go no further. I should point out that SPD sets my ram at 5,6,6,20 - miles out from what it should be.... this got me thinking...
Next I booted with SPD settings and used memset
http://rv.page.cegetel.net.perso.cegetel.net/MemSet.zip to see all the ram settings. I took a screen shot and saved the memset settings.
Then I rebooted changing back to manual RAM settings in the bios 4,4,5,15
When in windows I opened memset and changed all the settings apart from 4,4,5,15 to be the same as the screen shot at SPD.
I was then able to go right up to 440FSB before i suffered any issues.