HeadwayThemes is such a great product. Blox Themes is pickup up the ball and extending the Headway code base. That's great as I have many sites on Headway to migrate to Blox.

Still, if Headway 4 would be completed, that would be a leading contender. Headway is for serious WP site builders and does well with page builder plugins from Divi or BeaverBuilder.