Being that you are in zone 5, I'd recommend that you put them in the ground as is right now and plan to divide them, if they really need it, in the spring as soon as the ground can be worked.

I'm in the process of moving some 500 or so plants from a display garden and just last week decided that I will not divide or wash/disturb the roots on any more this season. I'm late for stopping compared to a lot of people here as our avg 1st frost is Sept 15. It could hit at any time.

When you divide the plants this time of year it triggers all the leaves to die and the roots too. Then they immediately start growing new feeder roots and leaves. However, they won't have enough time for that new growth to harden before frost sets in. The less you disturb the roots now, the better.

Taking them out of the pots and putting them into the ground so that they have better protection from the cold of winter is a good idea.

Never divide below 2 fan sections as you'll compromise bloom.

Thank you so much berry,
I will get them in the ground today.
I appreciate your help. :0)
cAROL