There are the obvious things like your energy bill and the water temperature going up without a strong chiller.
The more light you have over a tank, the faster plants grow. If you enjoy daily pruning, and don't really want to take a couple of days off per year, put lots of wattage over your tank.
The more light over a tank, the more nutrients are required by plants. If you are comfortable maintaining good levels of all nutrients at all times, go ahead and add lots of light.
If you are new to this, and especially with a new tank, I suggest to start "slower". Less encounters with algae that way.