do i have to get a new ballast?

i bought a 400 watt hps bulb and ballast and reflector and all that, and now i want to step it up to a 600 watt hps, will i need to get a new ballast or could i just put the 600 watt where my 400 watt is?

Im sure someone will correct me if I'm wrong but you cannot use 600 watt bulb in a 400 W ballast. They may dimmable ballast but in your case that would not work.

ok thanks il just have to buy the ballast as well then...