Okay here's my advice for your 180 gallon you plan on setting up.
Lights, you could get by with 3 black box units, running them length wise, but may need 4 for coverage running their length from front to back.
This depends on how you aquascape the tank. If aquascaped with your rock structures in the center, you could get by with 3.
Removing the lenses will help with light distribution and blending. I personally have mine hung around 12" above the water line. 60-70% blues and 20-30% whites.
With a 180, I would want to have two overflows, one in each back corner. I personally have a stock Marineland reef ready with the corner overflows. Each overflow has a "Durso" drains. The stock configuration had the returns coming up the overflows and exiting at the top of the overflow box. I converted these to emergency drains.
You don't need emergency drains, they are just a assurance in case of one of the drains gets clogged. So the DT doesn't overflow. (Wife, living room tank..... assurance! Lol)
In your case, I would at least have two overflows draining into your sump. Each needs a "Durso" to keep it from "toilet flushing" and keep the noise down. The way your tank's overflow is now, water will drop down the glass overflow (making a waterfall sound and then "gurgle" down the bulkhead into the sump.
