Try the 1.25x strap and play with ram speeds. I found I was limited by ram before being limited by my cpu multi.
These are useful voltages:
1.1v for imc/vtt or vccsa/vccio
1.65v for pll
Set vcore to 1.3v and try increasing cpu speed with ram fixed at 1333 or something like that. It's better to isolate components.
I like to stress with cinebench for something quick and some XTU while at it, then check for whea errors in the event viewer.