I think it's a total over kill. Light will have to be so far above so as not burn plants you would lose lumens. I think in a 3x6 area a 600 would work much better being you can get the light closer which mean more lumens.
Plants that are 2 feet away from light recieve 1/4th the amount of light recieved by plants one foot away. An HID the emits 100,000 lumens produces 25,000 lumens 2 feet away. A 1000 watt hid that emits 100,000 lumens yeilds 11,111 lumens at three feet away.