Wide blog theme for drupal
You could modify Best Responsive theme enlarging the page width. More precisely changing #wrap ID width from 960px to something bigger, like 1200px or a percentual value like 90%.

You can edit the style.css file and change the width from:

#wrap {
  width: 960px;
  margin: 0 auto;
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}


to:

#wrap {
  width: 90%;
  margin: 0 auto;
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}


You'll have to update some other elements width like #content and #sidebar using a percentual value and fix the sidebar background image.

Anyway the theme can easily be customized.

In this way the template is still responsive but on desktop the size is more wide.

I hope this will help.

Regards.