780i does easily 450FSB with the quads , keep the ram in sync to rule out stability probs there, though I benched fien here with P03 bios and 1200Mhz on the rams...

Sadly the reference design boards have big Droop/drop issues, me too needed 1.65 to bench at 1.53 volts (1.58 in winblows) which is horrific with the Qx...

Why don't you just try let the CPU burn in at 400FSB with 8 multi... then try to lower the Vcore gradually... but if ya keep the VID in mind it coudl well be that you need 1.5real volts to be even stable...

Looking at ya numbers you have a real bad clocker there requiring massive voltages...