Все решено!!! Тему можно закрывать. 
  
http://take.ms/Z8KlC --- вот скрин, что получается. 
Реализовано через контроллер категории, кому интересно вот код: 
$this->data['categories'] = array();
 
			$results = $this->model_catalog_category->getCategories($category_id);
 
			foreach ($results as $result) {
				$data = array(
					'filter_category_id'  => $result['category_id'],
					'filter_sub_category' => true
				);
				$children_data = array();
				$children = $this->model_catalog_category->getCategories($result['category_id']);
 
				foreach ($children as $child) {
					$data = array(
						'filter_category_id'  => $child['category_id'],
						'filter_sub_category' => true
					);
 
					$product_total = $this->model_catalog_product->getTotalProducts($data);
 
					$children_data[] = array(
						'name'  => $child['name'] . ($this->config->get('config_product_count') ? ' (' . $product_total . ')' : ''),
						'href'  => $this->url->link('product/category', 'path=' . $result['category_id'] . '_' . $child['category_id'])
					);						
				}
				
 
				$product_total = $this->model_catalog_product->getTotalProducts($data);				
 
				$this->data['categories'][] = array(
					'name'  => $result['name'] . ($this->config->get('config_product_count') ? ' (' . $product_total . ')' : ''),
					'href'  => $this->url->link('product/category', 'path=' . $this->request->get['path'] . '_' . $result['category_id'] . $url),
					'children' => $children_data
				);
			}