Since we are not really restricted as to when we can plant or transplant here, I'd wait as long into the fall/winter season as possible. It takes a long time for these to go dormant and in some winters they never do so fully. At least that has been the case in my gardens. I had them flowering in January last winter!

These are also pretty sun tolerant - I have grown them in full sun to full shade with the sunnier positions blooming more heavily and for longer and with better foliage color.

Mine does go dormant. It's in the coldest part of my garden, near the house with northern exposure. I couldn't move it before it goes dormant?

You could. But there is always a much greater risk of transplant shock if you do so before dormancy or while still in leaf.

Thank you. I really would like to move it before the ground becomes saturated with our fall rains. It's still very wet in that area of the garden in May so it makes it difficult to move it in spring.