300w may not be enough power depending on what and how you are shooting. I regularly use hot lights alone, or in conjunction with strobe and available light. Even at 650w, I find myself at the edge of the ISO 100 to 400 range with a 85mm f1.2 or 70-200 f2.8 lenses wide open. But I usually diffuse the light through a panel, and the light source if typically about 6' away from the model.
With that said, you mentioned that you have a small studio. If you will be using the light without any diffusion, and in fairly close, 300w may be just perfect. If you have more details on how you would be using it, we may be able to give you more specifics.
650w tungsten balanced with background ambient window light. Canon 85mm f1.2 at f1.8