Be sure you stock an extra bulb or two, as 600's are a bit harder to replace than the more common sizes, ie 400-1000, and generally more expensive. It's also recommended you have a back-up ballast. I just bought two entire 600 set-ups, figuring one would get me by should I need to wait for a replacement part.
Thanks man , they did not get any light or sun what so ever in there first week though .. so i ordered some 6500 k and 3000 k HO T5's 54 watt each and save em ... u shud of seen them before .. they looked really scrawny ... thanks to the lights , they've been saved .