i used to run thousand watters,
you do need air cooled hoods ideally, depends on your set up. however it is cheaoer and you get more lumens from two six hundred units than from a 1000 watt, the 600 unit is the most efficient at light for power output!
1000 watt lamps are good for depth penetration! something you wont need in a seven foot high grow room! pluss two six hundreds can disperse the light more evenly. dont get me wrong you will get good results under a 1000 watter, but even better for less cost under two sixhundreds!