Count Widgets and add Custom Class?

Hi I have got the basics of wordpress theme development down pretty well now, but I am currently developing a new theme that I would like to have a bit more functionality.

I would like to give the user the ability to change the configuration of widgets on pages through the admin panel giving them a number of styles. I understand how I would do this with html and css. I would assign each widget a custom class name like class=”frontpage-widget-1″ class=”frontpage-widget-2″ etc so the each could be styled differently. My question is how to I achieve this with php?

Can it be done when the sidebar is registered in functions.php?

Thanks in advance any advice will be greatly appreciated!