I purchased level 4, 7, and 8 along with the TG for my rising 2nd grader. I'm not 100% sure I want to completely drop phonics yet because, although my son is a good reader, he does still need some work on multisyllabic words. Hopefully, ETC will be helpful and not very time consuming.
So, maybe pick two or three levels. I definitely don't think it would hurt.