VVCh

Менял в catalog/controller/product/category.php

$sort_data = array(
			'pd.name',
			'p.model',
			'p.quantity',
			'p.price',
			'rating',
			'p.sort_order',
			'p.date_added'
		);

		if (isset($data['sort']) && in_array($data['sort'], $sort_data)) {
			if ($data['sort'] == 'pd.name' || $data['sort'] == 'p.model') {
				$sql .= " ORDER BY LCASE(" . $data['sort'] . ")";
			} elseif ($data['sort'] == 'p.price') {
				$sql .= " ORDER BY (CASE WHEN special IS NOT NULL THEN special WHEN discount IS NOT NULL THEN discount ELSE p.price END)";
			} else {
				$sql .= " ORDER BY " . $data['sort'];
			}
		} else {
			$sql .= " ORDER BY p.sort_order";
		}