Menu / Navigation plugin for a large wordpress site – recommendations please

I’m currently building what will become a rather large site, and I’m trying to find a good plugin to handle the navigation.

Currently I’m using the Mystique theme together with a plugin called ‘Nice Navigation’.

I’ve configured the top level of the custom menu to be displayed horizontally using the Mystique theme, which is fine.

My custom menu is then also displayed via the ‘Nice Navigation’ plugin in the right hand column, this uses javascript to display all of the top level menus in a collapsed state, with just the currently selected menu expanded.

This gives me the style of menu I require, however because it uses Javascript to do the collapsing:
a) It first displays the full menu and then collapses the nodes, it does it quite quick, but it is noticable which doesn’t look great visually. Also I fear as the site gets larger this will just get worse.
b) All of the collapsed menus options are present on the page, and I’m sure this is hindering my SEO efforts slightly as it’s cluttering pages with unecessary links and keywords that aren’t relevant to the page I’m trying to optimise.

Is anyone aware of a plugin similar to ‘Nice Navigation’ that only renders the top level menus and the menu options that are within the currently selected menu (without using javascript). I’ve been searching the plugins but not managed to find anything.

Thanks