Amazon's running a promo so before I ordered either Kobo or Boyue, I traded in one of my Kindles (the registered one, apparently a PW2 not a PW3) for a new PW3 for $35 + tax. The new Kindle was jailbreakable so happily, I now have collections support via LibrarianSync on the new unregistered Kindle. I will just register my other, older PW3 and use that for Amazon purchased content.
Thank you all for the recommendations. Certainly was interesting to research even if I ended up going a different route.