Incidentally, these are pics of some of the clematis. Many, like Bee's Jubilee, the President, Nelly Moser and Niobe are actually still in bloom in mid-October in Chicago.

Here is a link that might be useful: Clematis

JPW, I personally don't like to attempt to overwinter clematis inside the house for the reasons you mentioned with roses above along with the fact that the plants tend to get very leggy unless you have a window that gets lots of direct sunshine.

You said that last year when you attempted to overwinter them outside, that all except one died. How big are the pots your clematis are in? How did you attempt to overwinter them outside last year? Did you cluster the pots together in a sheltered location? Did you leave them sitting out in the open where they were exposed to the elements? You could attempt to cluster them together and place some sort of insulating material around the pots such as bales of straw or the like. Even if you had an unheated area where you could store the pots after they had been exposed to sub-freezing temps that took them into dormancy, that would be better as far as I am concerned than attempting to bring them inside the house. Do you have friends with uninsulated garages or even crawlspaces that could store the plants for you?

Personally, I prefer to bury the pots in the ground somehow. The pots need insulation, as Miguel stated.
But, if you can't bury the pots, I like the 'straw' idea. Cluster your pots against a corner in a sheltered area and spread a bale of hay densely over the pots. This should protect the roots and cause just enough heat to insure their survival.
Suzy