Northern Spicebush is actually a native plant for Georgia and should be just fine in Kennesaw. They can be a little difficult to transplant, but once established are pretty hardy.

I've heard various opinions on the hardiness of the Hummingbird Bush between zones 7 and 8, so it might be a tender perennial for the north Georgia area. You might want to try to find a sheltered location for it, maybe with a southern or eastern exposure.

I'm in Rockdale County. We have several Anisacanthus quadrifidus var. wrightii we planted in spring 2008. So far, they have thrived for us. We add a good layer of mulch for winter. Ours were slow waking up this year (May 10). Last year they were putting on growth in late March. They fill out fairly quickly once they start. As long as the plants are in a space that drains well, I think they should be OK. Also, I believe the more sun they get, the more blooms you will have. Ours are in dappled shade until 11AM, and then full sun until evening. They bloom nicely. Hummingbirds stake them out and battle to protect their stash :~).