Since a lot of people seem to be saying "why would you buy a Paperwhite if you want ePub support???", I just want to clarify. This concerns lending ebooks from my local library, since I want to support them and they use ePub predominantly. It doesn't concern any large amount of books.
Concerning the topic of this thread, I have started using Calibre and the conversions work splendidly from ePub to azw3. I find it a bit strange that people keep referring to ePub to mobi conversions - why would I use mobi on a Paperwhite?
Thanks to everyone that have replied, I believe Calibre will work wonderfully for all my conversion needs in the future.