Hi Beth,
While I'm by no means an expert on weight lifting in general, I guess your use of S&H depends on how strong you currently are and whether the weights you are using still challenge you. I would say that you most definitely would need to use something heavier than 10 lbs for the leg section. Do you do any other lower body lifting right now?
My own personal feelings are that in order to get an effective workout with these tapes you really need to be pushing your muscles to the limit. The idea of s&H is to build muscle mass and perfect your form, so you may see your form improving as you use your dumbells, but (again depending on your current level) I think you might quickly progress past the 10 and 15 lb dumbbell weightload.
Also, I know you said you don't want to, but I think barbell would be a great investment for you - you've already made that investment in the videos so why not take it a bit further? You could probably find a 110 lb dumbbell set for not too much more than the S&H series cost... again just my opinion! I really do like S&H and have seen my weights increase in the last few weeks. I hope this helps!
Lizzie