My N9 (Singapore version preordered) has been solid at: 1300mHz+1.275v and smart reflex on I get an almost instant reboot at 1.25v. I am thinking about trying 1400 mHz now.
Why go to 1300000 if I am stable at 1275000 (1300 MHz)? As for 1400 MHz I went as high as 1362500 but device reboots a few mins after testing. Oh well.