I've run anywhere from 400 to 1400 watts in a DR120. I'm using a 6 inch centrifugal with a speed controller to adjust flow. If you go with a 6 inch size it'll be more than enough for a 400. Not knowing your ambient temp, I hesitate to recommend anything smaller. I'm in USA and not familiar with the brands you mention. Better to buy a little over=sized, it'll give you options for more wattage should you decide to go that route.
HTH