Personally I just abandoned my Kindle library when I bought a Nook. That's not particularly helpful, of course, but it's what I did as part of kicking Amazon out of my life entirely. I started buying my books from non-DRM sources.

I will say this: you may have paid for "licenses" for those books, but you don't actually own them. Amazon can rip away your access to them at any time. Were it me, I'd simply pirate DRM-free copies of the same books. Though if you can successfully strip off the DRM and convert them to open-source formats, that's just as good and carries less risk. Every time I've converted ebook formats with Calibre it's done weird stuff to the text: letters incorrectly interpreted, missing punctuation, page breaks in odd places, and enough of them to be annoying. Something to consider. Maybe that kind of thing can be corrected but I haven't yet figured out how.