i am also setting up a tank of 1600 liters and i rueld this pump out. I am pumping 1.2m head height from my sump back to the tank so i think this pump would strugle to manage 400lt an hour but i have never used this pump before. I am thinking more along the lines of either 2 aqua medic eco runner 1200ltph pump (150watt each) or a single red devil 1450gph (65 watt) i think that skimping on a pump now would be a bad idea especialy when it comes to big messy fish such as rays because you dont want any nasty dead spots in your new tank or i dont any way. I am still keen to hear from other people in reguards to what pump they use on simalar size tanks.
Take your point on the NJ8000. Been looking into them some more and now realise they only pump 450cm of head! Not good. Now looking at the Aqua Medic 9000 they pump up to 4 mtr of head for 95 watts. Seems good to me. The Laguna that is also mentioned in the thread pumps 9000 at 3.7 mtr of head at 100 watt.