Blackwater question.

[NoMoreGoldFish]

I've been adding Indian Almond leaves and its extracts to my aquarium, I love the look and my fish seem more active with them, but my tank is well planted so I'm planning on getting brighter lights to counterbalance the blackwater effect. So now it raises the question, visually is there a difference between let's say 2 watts of light per gallon in moderately tanned water and 4 watts of light per gallon in very dark water? Because if they look the same, I might just add less extract to my water and save on getting new lights.