Не дождался я ответа и докопался сам. Все оказалось очень просто!
Находим файл /catalog/controller/product/category.php
И меняем эти строки:
$this->data['sorts'][] = array('text' => $this->language->get('text_price_asc'), 'value' => 'p.price-ASC', 'href' => $this->model_tool_seo_url->rewrite(HTTP_SERVER . 'index.php?route=product/category&path=' . $this->request->get['path'] . '&sort=p.price&order=ASC'));
$this->data['sorts'][] = array('text' => $this->language->get('text_price_desc'), 'value' => 'p.price-DESC', 'href' => $this->model_tool_seo_url->rewrite(HTTP_SERVER . 'index.php?route=product/category&path=' . $this->request->get['path'] . '&sort=p.price&order=DESC'));
На вот эти:
if ($this->customer->isLogged()) {
$this->data['sorts'][] = array('text' => $this->language->get('text_price_asc'), 'value' => 'p.price-ASC', 'href' => $this->model_tool_seo_url->rewrite(HTTP_SERVER . 'index.php?route=product/category&path=' . $this->request->get['path'] . '&sort=p.price&order=ASC'));
$this->data['sorts'][] = array('text' => $this->language->get('text_price_desc'), 'value' => 'p.price-DESC', 'href' => $this->model_tool_seo_url->rewrite(HTTP_SERVER . 'index.php?route=product/category&path=' . $this->request->get['path'] . '&sort=p.price&order=DESC'));
}