Nav changes on each page

[thinkofmedia]

I'm trying to replicate a similar navigation www.overstock.com use.

Basically I'd need a nav bar with sub categories show on the home only. And then an alternative nav bar on the category pages with the sub nav in the top bar.

Any ideas how best to approach this?

Could I maybe do two nav bars in the back office and hide one from the front page and then unhide for the rest of the site.