Moving them in the fall will not hurt them. The only consequence you may have is you may have limited or no flowers the next year. If your plant is large(more than 20 eyes), I suggest you take this opportunity to split it up in two and replant them as 2 plants.

I moved Garden Treasure a couple of years ago in the fall,when it was already fairly large. Didn't divide it - just took the biggest root ball I could manage, and tried not to shake off too much dirt. It bloomed well the next year. I moved Morning Lilac last fall. It was a relatively small plant, just a couple of years old. Again, I just took as big a root ball as I could. It is blooming well this year.