How many watts for which type of light modifier?

Increasing the ISO is a camera adjustment, not a light adjustment. If I have everything dialed in, but need to modify a light, adjusting the ISO makes everything change. It may work in some situations, but is not a fool proof way to do things. Besides, if your buying studio equipment, your going to want super clean images, adjusting the ISO is hardly the place for that.

Usually the problem is too much light, not enough. Heck my 1200 mono will cook the skin right off a model if I let it.