It's complicated to change those divs, because they are set up in the functions and core files of the theme. So, you have to remove actions,etc to do that.
It seems ridiculous that a theme that claims to be responsive does not have a header that is responsive.
After trying a child theme with styling and function changes, etc, I have reverted to using the original theme. This is how it looks now:
http://claritysound.net/wordpress/
I picked my own logo in the theme customizations (which, by the way, disappears when you create a child theme - there is no longer a way to add a logo in theme customizations!), and it's crammed in with the site title on top and description below. It is not at all responsive when changing the browser size.
I like the theme otherwise, but this is crazy. As I said, with the divs being created by the functions and core files, it's hard to change anything. There must be a way to do it, but everything I've tried just causes more problems. And besides, those kind of core changes shouldn't be needed with a theme that claims to be responsive!