yeah, just leave the multi at 8 and adjust the fsb to 400 (or 1600, however that bios does it). the 6750 can probably do it at stock voltage. if not, bump the voltage to around 1.35 and try again. if it fails, try bumping the northbridge voltage a notch. That should get you there. that proc oc's pretty easily to 3.2 or even 3.6 and beyond.
ah ok, i gotcha. I tried leaving the memory timing set at 4-4-4-12 which is which is what the stock timing is, however i was noticing that the computer was hanging alot for maybe 5-10 seconds when I was trying to open programs and stuff like that, so I loosened it to 5-5-5-15 like you said and it seems to be fine now. I ran a prime95 test for about 8 hours and it didn't crash and temps didn't break 54C