Also, the 5000k bulbs aren't that bad either. They will work well for the lower end bulbs. Now for the higher end to give the total light a good mix, in color, as well as appearance.
You can go as high as 12000k as well. The range for planted tanks can go from 5000k to 12000k. 6500k is a good in-between, as it is more like daylight. So if you find 12000k and no 10000k bulbs, go for it.