As already mentioned in the thread, newer LED fixture & DIY options are appearing at a breakneck pace. I finally jumped off the fence earlier this year & decided on a high power 10 watt LED array build. These LED arrays, or multi chips are available in increasingly high wattages, over 100 watts per chip and some of the 100 watt chips are capable of handling twice that power, i.e. over 200 watts. They are also now available with different LED colours suitable for our hobby combined on the same chip.
Here's a photo of some of the components I've used. 10 watt LEDs in 3 different colours. Decided not to use the optics, they were the wrong size (made for 20 watt & larger LEDs) & the glass lens is way too heavy. I have 27 of these LEDs on my fixture & if I used those optics it would weigh a ton. One of the reasons I chose to build this way is to save weight by not using large heatsinks. I'm getting plenty of punch & very good colour blend without optics & the fixture 8" above the water. I've found the 10 watt LEDs to be a great balance between power & ability to blend colour without needing too many of them.
I have a thread of the build going in the DIY forum here. I suspect that if you were to disassemble a Kessil LED, you would find similar components, a high power LED, probably in the 30 to 50 watt range, with optics & fan.