We do not plan on carrying 4000K strips, as the 3500K strips are very close to the 4000K strips, and a 4000K CCT can be built using a combination of 2700K and 5000K strips:
2x 3500K + 1x 5000K= 4000K
3x 2700K + 3x 5000K= 3820K
2x 2700K + 3x 5000K= 4080K
2x 2700K +4x 5000K= 4230K
Of course, if more people want 4000K, we will reintroduce it. As for 6500K, we can produce any CCT in the Samsung LM561 line on a custom basis, with a minimum order of 25 strips and 30 days lead time.