Wee update:

Got 185x23 (4255mhz) stable with 1.475v set in bios.

Anyone else getting really random vdroop? Setting 1.44v in bios gives me 1.424v in cpu-z under load, setting 1.46v in bios gives the same. Setting 1.475v in bios gives 1.456v real @ idle, 1.44v under load. Still that means i've nailed 185x23 =4.25ghz 10hr prime stable with 1.44v, which is not bad i guess. Now going for 4.3ghz with 23x187!