I myself would probably go with 1000 watt hps's, but as smokey said, that is a lot of power to be using just on lights, also you are going to have to majorly worry about your exhaust system because this is going to create a very large amout of heat. You are going to have to make sure that your current wiring in your location can handle the ampage that you will be pushing with your lights, exhaust, fans and other equiptment.
Lastly you are going to have to control the smell of all that growing bud. You are going to have to have a supersized carbon filter, because you will not be able to just vent this outside.
I have no idea of your growing experience but unless you are a very experienced grower, I would suggest you to maybe cut your plans in half, because manning to 60 plants is no easy task.
Most of all Please take care, and tell no one at all of your plans. Good luck