Agile and Classik are both setup the same way….with the header on the left. As mentioned before, you can definitely have the header up top, but the only way to do it is to unhook the current location and add it to a different location. This can only be done through your functions file as all Genesis Hooks are done this way – http://www.studiopress.com/tutorials/hooks
You could also take a look here at this tutorial by Carrie Dils on moving the header – http://www.carriedils.com/web-development-blog/genesis-framework/move-header-footer-genesis/948
The only other thing you would need to do is customize your css.