more than 3 sidebars possible?

You should be able to do this with any of the starter themes--I'm pretty sure it'd work with Framework or Zen, can't say for sure on others--anyway, to add areas to your page, define new regions for your additional sidebars in your .info file, add them in template.php and style 'em up.

Two good ways of going about this:

1) use a grids based theme like Ninesixty (define regions in info file, add to page.tpl.php), OR

2) start with a convention starter theme like Genesis and use Panels to divide up the page.

Depending on your level of experience and time available arguably using Panels is by far the easiest way to get this done. Ninesixty and the other grids themes are very good but can take some time to get your head around. In Panels you can build your own panel layout (theres a special panel type that allows you to define rows and columns).

The main drawback regarding panels is the columns don't collapse, whereas some of the grids based themes can do collapsible sidebars, such as Ninesixty and Bluetrip (any of them could potentially if you know a bit of PHP, but Ninesixty has by far the best implementation of them all).

I assume you know your audience all have large resolutions because going over 1000px is going to cut out a huge proportion of visitors.