500 watts for only 10k lumens? That is TERRIBLY inefficient if true. For example:
500 watts = 19 CFLs for a total of 30400 lumens
400 watts = 1 HPS for a total of 55000 lumens
Also, regular T12 40w flourescents run anywhere from 2400 to 3400 lumens each. I think your numbers might be off, but if they aren't, you might want to consider getting some CFL's or even an HPS to save yourself some money and quadruple your yield.