Widget area - after every odd widget inside close and open div


I would really appriciate a coder advice how to do that. I have one widget area (testimonial), you can see it at bottom of my page. I have custom widget - which you can check here(and js here) to create a testimonial.

I'm right now registering the widget following way in my functions.php:

function widgets_init() {
	register_sidebar( array(
		'name' => __( 'Testimonial', 'kybernaut' ),
		'id' => 'testimonial',
		'description' => __( 'Zde vložte maximáln? 3 Image widgety', 'kybernaut' ),
		'before_widget' => '<div class="span6"><div class="row-fluid">',
		'after_widget' => '</div></div>',
		'before_title' => '',
		'after_title' => '',
	) );
add_action( 'widgets_init', 'widgets_init' );

I need to get following output (which will be repeating until there are no more wigets to display):
html result of wifget (sample data)

So I need to:
- open the row div <div class="row-fluid push-top push-bottom">
- echo two wigets
- close the row div, print hr and open new one div: </div><hr><div class="row-fluid push-top push-bottom">
- and to the second set of widgets (3rd and 4th) I need to insert to the div with class "span4" one class "pull-right" and to the "span 4" I need to add "text-right" (as you can see in html result above
- third set of widgets (5th and 6th) needs to be as well without those classes, fourth with... repeating until end of widgets in this widget area.

Could somebody give me a hint how to modify the widget_area before printing? and how to insert those classes into the custom widget print? Thanks for your advice and hope, that's not too chaotic.