2 600watt lights in a 4 foot wide by 4 foot deep by 6 foot high tent would be a lot. If you had dimmable balast and could dial it down during veg, and early bloom it would be nice to have 1200 watts for FULL bloom, but would be a waste of money up until then in my opinion. I'm having to keep my lights (1200watts half in cooltube) about 2 feet from the plants to keep the leaves from bleaching. You would DEFINITELY need an A/C to keep it cool. 1200 watts creates A LOT of heat. I've got a 6' x 12' room and the AC runs constant.