I am using their 8K bulbs and love them...
Brighter, better color... It appears
to have the same "white" as the 10Ks (e-bay) I had when looking at the lights, but in addition the reds are redder and I see more yellows off the plants. (I'm trying to say, the light ain't yellower, but gives better yellows and reds - does that make sense?).
My plants are enjoying the change as well as the thread algae
I had an outbreak I'm just now (I hope) getting under control with the change in intensity and color (It was like "WHAM" - where did that come from???).