I've been somewhat happy with the Prime's over my tank so don't intend to discourage you from it, but the spread is not great. Even with two, they put a pretty focused beam down in a 12"x 12" area with each fixture. That's not to say they're not powerful enough to fry even some SPS at full power in that 12"x12" area, but just that you'll get lots of shadowing issues in the outer areas of the tank as things fill in.
Another good and proven option on the cheap if you're looking to save some money: one of the best looking tanks I've seen in person (huge acro colonies growing literally out of the water and over 10 years old to boot) was running Ocean Revive T247 lights. A single T247 costs less than a single prime and would cover the entire area of your tank with much better spread. With just LPS and softies, a single Prime raised up a bit and running at 100% would be fine to get you started, though, if you aquascape so that the corals are mostly in the center two thirds of the tank