If your epub's aren't drm'd, Calibre indeed is an easy way to convert them to a format that the kindle will read, and it's easy to sideload them to a kindle using the software too. If they are drm'd, well, that takes a little more work, but even then it's not that big a deal if you look in the right places.

For that matter, since you say you transfer books from your pc anyways, I'd strongly suggest looking into Calibre just as a way of organizing what you currently have anyways, even if you go back to using the Kobo.