ok

You say you have a space 6' x 8' that is 48sq ft that is very large, keep in mind light is everything, more light better the grow. The best way to figure this out is 400w hps or mh = 3'x3' or 9 sq. ft. 600w = 4'x4' or 16 sq ft. 1000w to big for your space NOT ENOUGH HIGHT you will burn your plants, for a space as large as yours you could put 2- 600w HPS and have a great grow room, CFL's or florecents won't cut it in this large of space, you will end up with medoker plants with small buds. LUMMINS determin everything, the more the better.

Also the investment in HID lighting is well worth it, one ounce will pay for it. Out of a space that big you could get 2 to 5 Lbs every 3 to 4 months.

also you could cut it in half, have one space for vegitive light and the other for flowering using 2 HID Lamps