I would definitely look at renting a par meter or if you have a local club that has one borrow it. Then you can get an idea of what you are working with and where your hot/cold zones are. When you know the light levels all over your tank you know what to put where and know what you need to add. Our eyes are really bad at guessing. We have a built-in "f-stop" iris in our eyes that opens and closes without our awareness so it's hard to tell by just looking.
lots of factors affect par beside the actual light. Pigments in the water, the distance of the fixture. I am about to set up a new system after a 15-year absence. I have my lights but won't build the aquascape until I fill the tank and take par readings so I know how high to place things.
I am actually going to purchase one. In the grand scheme of things, they are not expensive compared to the coral and power heads. They are especially important when you don't have a proven light setup that you know works!
I am a big fan of metal halide. I have looked at several LED setups and Kessil high-end LED's online and several in person now. Metal halide is where I went back to. It is what I used to run and it looks so so good. I really tried to talk myself into LED. There are so many things I like about LED. I love everything about them except for the light.
