Centered logo

1. Give the logo a larger height from the theme options (let's say 100px in this example).

2. Use the custom CSS code from the manual (the one about having a larger logo - and use it for 100px).

3. Add the following custom CSS code also:

#main-menu {
  height: 160px;
  position: absolute;
  top: 60px;
  left: 50%;
  margin-left: -350px;
}
#logo {
  height: 43px; /* real logo size */
  left: 50%;
  margin-left: -90px;
  position: absolute;
  width: 193px;
}

This is a starting point. Of course, when the scrolling is done, everything will look bad, but you can configure things in that point as well, using the .smaller class which is added to the header.