I want to build this
Did you end up building your spray bar??
To answer a few questions you had above, yes a spray bar will help reduce dead spots and help increase flow, but I doubt it will be enough flow to keep the entire tank circulated. Depending on what size aquarium you have will determine if you need a power head or not. Right now on my 75 gallon I am running to large canister filters and a circulation pump. I bought some SunSun circulation pumps (wave makers) for my 180 gallon and they work amazingly. Much quieter than my Koralia, and a lot cheaper, I bought the one with dual outlets and two impellers per pump, think they are rated at like 1,800 GPH and were around $15 each so I was able to get both for less than one Koralia.