I asked this question to RightStart myself. They responded that they recommend Video Text after completing their course.

Yes, Video Text is our first choice after RightStart as they have the same philosophy as we do of helping the children see the reason for what they are doing something and not just memorizing the algorithms. However, if you have another program that you already own and it worked well for an older sibling, please feel free to use it. Once a child comes through RightStart he/she is thinking mathematically at a higher level and can usually adapt to most curriculums since he/she has such a solid foundation.
Nancy