Thanks Dale! Unfortunately BetterRed is correct and I am on a Mac, so I can't try out Atlantis. Don't have Parallels at my fingertips...
QuarkXpress, surprisingly enough, does seem to still be around. They have a whole little ePub exporting thingie, just like InDesign, and it
seems like they have a whole "reflowing view" where you can see your content in a linear fashion--one of my main gripes with ID.
...That said, it's $850. Yikes.
Now, the last time I looked at Sigil it was this seemingly abandoned project with some issues (very strict markup validation & "cleaning" which I did not appreciate) but it seems like it's come a long way thanks to some hard work from some people. I mean, it checks a number of boxes...I wonder how hard it would be to implement a styles system and some other things. Too bad I'm allergic to python.
But that's a bit off, so any other suggestions are welcome