You could go with the one 600 & side light with one double tube fluorescent on each of the four walls (shop light with grow lux plant lights) & hang a few CFL's to bring up the lumens cheaper to purchase & cheaper on electric. I like to lay a few (tube type) fluorescents on the floor, on their backs aimed at the undersides of the plants too. Besides the grow lux & special plant fluorescents, you can use cool white (blue spectrum) for growth & warm white (red spectrum) for flowering. I see you started your seedlings under fluorescents, don't underestimate them to combine with other lighting throughout your grow. Its a good mix & a cheap way to raise the lumens, anytime you need to up the light output, throw in another fluorescent or two. Keeps the temps down compared to HID's. Don't forget to figure in electric usage for cooling.