If you are considering moving away from Evernote, there is a useful app that might help: ExportNote. The “Premium” version is reasonably priced and can be used to export notes as PDFs (or HTML) into a set of folders that mirror your Evernote stacks and notebooks – your hierarchy inside Evernote. You could then import or index that folder hierarchy in DEVONthink.
YMMV, but I found this to be pretty good tool, especially if you use stacks. The export takes a while, but it’s one of those things that you kickoff and then go watch a movie. The app works offline and uses your local Evernote database as the source, so be sure to sync Evernote before using the exporter.