Can you go higher, at 1.25V? <1.3V is fine and, while 1.25V is pretty high for a fairly moderate OC, the middle ground shouldn't matter too much - the upper end of OCing vs the 'stock' settings would be my main consideration.
What are your auto voltages at stock? Each board handles it a little differently.
IIRC, typical is around ~1.12-1.15V. If your boards starting point is higher (say 1.15V+), then your OCing voltage would likely need to be increased proportionately.
From there, see what kind of clocks you can push @ 1.25V. You have a little headroom, but not a ridiculous amount. Perhaps you can net 4.4-4.5GHz @ 1.25V too, at which point, that's a pretty decent OC on a 4770K.