You could add – “background-position: center top !important;” to your #header in the 2 responsive sections of your css file. (bottom).
Also, you will need to make the logo area clickable so you can add the following –
padding: 20px 0;
You may need to add !important at the end of some of the css rules.
If you don’t want to deal with the code you could try a plugin by Nick Croft that handles this automatically – http://designsbynickthegeek.com/plugins/genesis-responsive-header