FWIW, i ran that same fixture years ago when i first started in the hobby. granted my tank wasnt 30 inches deep, but that shouldnt be a huge issue in the beginning. Rather than dumping more money into lights when you dont even really know what you want to keep, maybe it would make sense to just use the pcs that you have. as long as you keep your corals higher up in the tank, and stick with mostly softies and lps you will be fine to start.
in a few months when you have a better idea of what direction you want to take, you can always buy a nice(r) fixture. but rest assured, you can absolutely grow corals with what you have right now.