The Tbred A is holding you back from overclocking, lol. Up the Vcore slowly and get a good HSF. Don't go over 2.0v for sure with air cooling.
:EDIT: If your motherboard can even go to 2.0v that is. Also, post what kind of PSU, mobo, and RAM you have. This could also be an issue, as PSU, mobo, RAM, and cooling are the 4 essential ingredients to a sucessful overclock. Also, every overclock is a "maybe what-if" situation. No two systems will overclock the same even if the components are all the same. Some luck is involved.