What you plan is not a bad choice, but a lot comes down to what you want to keep, and what do you want to get out of the system.
For example, if you want a tang in the system, you'll be much better off with a larger and longer tank. If you want SPS corals or clams you might want better lighting that what comes with the system. Some people like to pick and choose every component that goes into their system. If your that kind of person, then an all inclusive Red Sea system may not be for you. On the other hand, if you want something you can just setup and run, a Red Sea system might be just the system for you. There is no right or wrong answer here.