You could have made a better choice, I suppose. And some authors/editors do deserve the money.
Pirating is not necessarily resisting. Are you taking money from authors who really really need it? Or are you taking money from rich CEOs who are worsening the environment, ruining future generations, slaving, etc?
Yeah, Calibre is the way to go. KoReader is basically custom built for Calibre, and includes things (missing from the base kindle firmware) like native metadata retrieval.