As mentioned depth is not an issue. I have an Ehiem myself on another tank and have found the output from the spray bar quite powerful. I would experiment first before buying a powerhead. It would be worth trying to allow an area of low flow to allow them to rest if required, between rocks or something. I would also recommend using one of the Korella pumps usually used within the marine setup. These are quieter and use less power than the equivalent powerhead.
They will breed in as close to a cave as possible. The male which is a mouth brooder will sit in the cave and look after the eggs. The fry once born would probably need a quiet area in the tank. There will of course be some parental care from the parents. We don't know yet if these guys produce dummy eggs for the young to feed on as with some of the other Snakeheads.
Another point to make would that when they breed in the drier season the flow may be greatly reduced due to lack of flow from the mountains. So when breeding the water may well be shallow and almost stagnant. This is of course just another one of my theories with no proof
DarkEntity. I think its the Pulchra's that like to swim in the flow, even then they don't like it two strong. Kewskills has four and prior to adding a power head they all swam mid water, as soon as the additional flow was added the all went low.
I have my Ornate's separated at the moment while I sort out their more permanent home. I will experiment with the flow and let you know.