if the voltage is supposed to top out at 1.425 then i wouldnt go over that. I had a pentium D 820 that i got to 4 GHz stable for CoD4, but it was operating at 1.44 vcore. the max was supposed to be 1.4. after about 9 months of running 24/7 it became unstable so i scaled back the speed. ended up dropping to a max OC of 3.81GHz because id damaged the CPU.
Gigabyte's UD5P made it all the way up to 3.4GHz without a bump in processor voltage, but 3.6GHz required 1.4V, and 3.7GHz 1.45V to maintain stability. Those voltages are still well within the realm of what's reasonable, even for modest air cooling. http://www.techreport.com/articles.x/16702/8
Yea...I'm running mine at 3.725Ghz wit 201.3x18.5x1.475. No problems yet, scoring high on vantage (11688 with performance edition) Can stand in place FFTs