Get a 600 watt with an extra wide reflector - I used to grow 4x4 with a 600 all the time with one. With that limited of a space you are going to have a hard time cooling 1000w without a really good ventilation setup. I had problems just keeping temps in line on a 600w system with an air cooled hood. 600W will grow more than enough bud for one or two people - only reason I can see to go 1000 is if you are growing to sell.