Looks like a start. I'd say 2 plants would do well in there, or maybe something like a party cup SoG. There are so many ways to go about it, just depends on what you're looking for. You can turn anything into a growing cab, and since I started growing indoors I see life through emerald colored glasses, so to speak. Everywhere I look, I see potential cabs in everyday items, and find myself constantly trying to figure out how to repurpose and recycle junk into components for my grow. 300w actual, and you might need more than PC fans, or maybe not. I guess it depends on the amount of air they move once all hooked up. Just make sure you have a flexible lighting setup, so you can reposition light for best coverage on your plants, seeing as CFL's power diminishes greatly with distance. But yeah, get cracking and soon you'll have a cab that I'm sure you'll be proud of. How productive it is, well that will be up to trial and error mostly, seeing as no two grows are exactly alike.