You don't need nearly as much light for vegging as you do for flowering, and you should perhaps look into getting some T5 fluorescent lights, at least for vegging. They're more efficient and better for young plants than MH lights. If you live anywhere near canada, your basement will lose a lot of heat to the ground, pretty much all year, so you're not too bad off as far as temperatures. Plus, in the winter you'll have nice warm floors.

Do you have any natural gas or propane appliances in your basement by any chance? If so, these can help boost your CO2. For instance, you can get a gas hot water heater to vent directly into the basement. A furnace, though, would use way too much oxygen to be able to vent that straight into your basement.