Have you tried the various themes? Each have their own style of navigation menu. They are all a little on the smaller side though... Go Central does not allow any HTML/CSS changes to the header section.
A custom HTML section below the header can work... I have done this. Understand that there will be a small section of whitespace between the HTML section and the header (and below). Also need to experiment with look and feel if website is also targeted to small devices like cell phones and ipads. You would also have to duplicate/copy the HTML section over to the top of each new page. The HTML sections allow CSS also... :-) P.S. If you are developing the site on the go central name.godaddysites.com address and then when finished change it to your final name.com, you should update the menu links in the HTML to the final web addresses of the published pages.