Well shucks. That settles it. I'm going to plant them in a large pot with a bamboo trellis. I'm very upset at my local greenhouse, this year they aren't labeling their plants, just telling us what they are. Maybe I'll luck out and they'll bloom all summer? :)

I have been finding the COTW search engine not to be entirely accurate. Twice I used it to search, once for shade tolerance & the other for a No ID & found errors in both. For example, a very common Will Goodwin is not being listed as having white/gold/yellow anthers with either blue/purple tepal. If you search w/o the anther color he shows up with blue as a tepal. So I wouldn't bank that all the possible cultivars would be listed in your search.

Might be 'Candida' or 'Miss Bateman' if the stamens are redder than that when they first open. It is hard to say, there are so many white large flowering hybrids (group II)

If you have purchased it this spring, I would go back and look at the various tags still in pots at the nursery where you bought it. Or use process of elimination to figure out what it might be when comparing to your list. Or just enjoy the flowers and don't worry about the name. You can figure out how to prune it based on when it blooms in future years. Regardless of type it will be encouraged to grow healthy roots if you hard prune it the first spring or two. There are a couple of reasons it is difficult to ID photos of young plants. Color is difficult to judge on-line since both the camera and the computer monitor can alter it. Small plants in pots from the nursery may be blooming earlier than they typically would, having been forced, and the flowers on young plants may not be the size or petal count of mature plants. Also, IME clematis at Lowe's can be mislabeled, perhaps from the nursery and perhaps from customers pulling out the tag to look at and then not returning them to the correct pot. And there are lots of purple clematis, though perhaps fewer that also have the reddish brown anthers as on yours. If you want to try to ID yourself, you can go to the Clematis on the Web database and do a search. Just fill in the things you know and leave the rest blank.