I started with a 400 HPS for flower and changed up to 1000HPS. More than doubled my results. More than enough for my 4' x 6' room. It kicks ass. More light more better more buds. Wish I had your room . You need about 3 or 4 1000's and some light movers and a ass load of plants. A 1000 will cover 7 x 7 to 8 x 8 foot square. Yield will be the most you can get if other things are right too.