You need to calculate the square footage of your grow space and factor in what HLG recommends for that amount of space. You can’t cheap out on this; there is no replacement for adequate light. All of that said, you could do a fine job using MH/HPS (which is a lot cheaper) but heat management and electrical cost is more of a problem.
I would suggest you got to the HLG website when it comes time to order.
Also: you might want to stick your nose in this thread and talk to the guru there: