My understanding is that maximizing the surface area of the nickel is vital to achieving kilowatt-scale output. The smaller the particles, the greater the surface area for a given mass of nickel.
Windflier, I suspect they are limiting the size of each E-cat right now due to safety/control issues. They've described how earlier experiments gave power outputs a good deal higher than seen in the public demonstrations, to the point that they were concerned about an explosion or overheating and so on. So it's probably better to daisy-chain small, easily controllable units at this point than try to build a great big megawatt class reactor whose reaction chamber is too big to quickly adjust or shut down in an emergency.
I imagine we'll see a lot of refinement as real engineering resources begin to be applied to the E-cat technology. At this point it's just the inventor and some academics I've seen involved with the E-cat, not really industrial/commercial types, so far as I've noticed. Getting it to produce electricity, and to serve as a powertrain for vehicles, will take some work.
And for all I know something like the vibration of a vehicle in motion might wreck the reaction process (I doubt it, but I'm just saying there could conceivably be some kind of show-stopper for some applications). Still a lot of unknowns at this point. But I am hopeful.