The 10000K is going to appear brighter than the 6700K. I just changed my bulbs from 6500K to a dual daylight 6700K/10000K. I thought I was going to have algae problems because the 10000K bulbs were so much brighter than the old 6500K bulbs. Since I got the same wattage as I had before, the wattage was the same to the plants, so no algae outbreak. Although the 10000K is brighter than the 6500K-6700K to our eyes, after getting used to them, they don't seem that bright anymore. My plants are growing very well.