Ebook Management Tools for the Mac?

I’ve had to restart my computer, twice, when Calibre screwed up my computer and wouldn’t let me forced quit.

I need to be able to convert drm-free azw files to epub, to be able to read them on my e-reader.

I would also like to be able to convert html files to epub, for the same reason. I can easily convert them to txt, if that helps.

I would also like to be able to strip bad formatting, correct metadata, etc.