PowerCMS and Contribute
Contribute can only handle static HTML pages. I don't see any coexistence between PowerCMS and Contribute. Contribute has a few more features than PowerCMS but it costs more and editor/admin users need Contribute to be installed on their PC. I have a lot of customers working with Contribute, but there are also many, that don't want to spend that much money. For them - I guess - PowerCMS seems to be the perfect alternative.