You would need a dangerous quantity of CO2 to not be wasting tons of light in there. 400W would do really well in that space. 600W would be a little bit of overkill but still doable. But 1000W is just a waste.
like he said 12/12 from seed or sog and your golden. shit even scrog 1 plant using a screen a little . you will see like a 7-10 degree F temp difference from ambient temp with a 440cfm fan. try it and see how your yields are. there someone on riu that grows with a 1k in a 3x2x6 and he does just fine. his names jigfresh.if you did a sog or 12/12 from seed or clone youd probably be better off. Itll keep your plants as short as possible. Like stated above you dont want to bleach your plant.
Also do you have central air or a dedicated a/c for the room thatll be in? Because unless its very cold where you live right now itll be hard to run that with just a cooltube and a fan.