Question about having 2 600w HPS lights

I'm going to buy 2 600W Hps lights with a lumatek ballast and want to know if there is a bulb that I can put in there ballast for Vegation or do I have to go Buy separate the 400W metal Halides. Idealy I would like to just use the 600W ballasts. Is this possible???? Thanks!
 
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