Hay mate sorry for late reply for some reason it didnt come up in my alerts that someone replied, I have been using HID lighting for years so unfortunately I do already have HID lights,If you have not purchased an HID yet, I suggest you explore PCB lighting, ie; quantum boards. I'm getting fantastic results, and have stopped using my HID.
I also heard that 600W is the most efficient way to go.
Check out Migro's youtube channel and watch their videos; very enlightening