Center Menus?

First of all I love this theme, it’s very clean and efficient.

I kind of hate how the menus work, and would like to possible center them or expand them to take up all of the room. Having leftover space at the end looks very awkward to me. I tried a few things in the editor but this is a little beyond my ability, is there anythnig I can do about this?

Here’s my site for reference http://www.thesportswizard.com

Thanks!