Sorry buddy, I hate to be the one to tell you this...
You bought the wrong mainboard if you want to overclock. You've already reached the maximum of what that board is capable of.
The H67 chipset can only overclock +400MHz Turbo. That's what you have already done.
The P67 chipset can overclock to a maximum of 57x multiplier or whatever your particular CPU is capable of, whichever is lower. This is what you should have bought.
1. Usually, overclocked performance doesn't scale very well. If you overclock 20%, you might get 5-8% performance increase. There are exceptions, obviously.
2. Using CoreTemp (or another program that can tell you individual core temps), keep all cores below 75ºC at all times. If it goes above that, back the overclock down.