I dont think it really matters too much how dark you paint the ceiling. Movie thetarers use black and if you are gutzy enough you can even use black.
Just find a color that will blend in the room real nice and will help darken the room some. If the room is too dark you can then go a bit further with your design and add a few wall sconce lights. They make a great accent to any theater room and wont be too hard to add or too expensive if you need to bring in a pro.
I am thinking of leaving my ceiling white for the time being and just painting the walls a red sandy color. It will be a lighter then maroon red.
If there is still too much light in the room I will then opt to paint the ceiling a darker color, mabey black!!!!!! I am too scared to do that right off the bat because if I eventually need to sell the house it might be a bear to paint over the black!