Go to the article section of the site (link in my sig) and read about cycling your tank.
I would put all 80lbs in the tank and you may find you want more then that. The cycle process can take several weeks. I would get as much base rock and you can and then buy a few pieces of LR
to seed the tank with.
What kind of lights do you have and what kind of filter? The glass tops are not a good idea for a SW
tank. They will cause you to have pH issues. Open top is much better.