If you want 3 fixtures on the top then I guess it will be fine. Some people don't like the clutter lol.
As far as watts per gallon thats' not a very good way to determine the lighting really, depends on the type of bulb and light output rather than "per gallon".
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.