You can definitely stick with just the two for the entire flowering. They have a lot of additive products that you can use to tailor your grow as desired, but they make it so they aren't necessarily needed.

I was looking into Overdrive and Big Bud myself, but ended up going Botanicare and General Hydroponics mixed, so never bought them. They definitely looked good, and I definitely will get around to trying them.

You will want to stop using Superthrive sooner or later (probably sooner unless you have a N deficiency). It has a high N content and that is usually not needed in flowering.