For Cambrige, two special requirement, GPA: >3.3; TWE:>5.0; For Hass, I am not sure, maybe GPA 3.0.
Last but not least, it is definitely not bad to have a pro for writing essays, but you yourself should dig into yourself deeply first. The deeper, the better.
Your background is good, the rest depends on your GMAT. cambridge and ivey's application is not difficult, but berkeley is quite difficult for chinese, especially for you from mainland!