some digital will do both mh and hps and some wont suggest you find out from the manfacturer first, or if your going with 600 guess it really doesnt matter as your stuck with conversion bulbs from what ive seen, and if your planing to use that entire 15 by 28 space you need about 21000 watts of hid lighting hope that generators a big one.
the 1000 watt light is your best light for intensity and if you was going to grow large plants for max yield would pobably use 1000 watt lights.
it is a big investment and big risk for one grow but if you have decent luck with germination you could easily have 50 females from 100 seeds and could veg for 2-3 months and put 4 large female plants under each light obviosly you will not have enough plants or lights to even come close to using the entire space.