Hi,
You have to edit these lines, to change the display in the product page, and product listing:
if($this->params->get('price_with_tax')){
echo $this->currencyHelper->format($price->price_value_with_tax,$price->price_currency_id);
}
if($this->params->get('price_with_tax')==2){
echo JText::_('PRICE_BEFORE_TAX');
}
if($this->params->get('price_with_tax')==2||!$this->params->get('price_with_tax')){
echo $this->currencyHelper->format($price->price_value,$price->price_currency_id);
}
if($this->params->get('price_with_tax')==2){
echo JText::_('PRICE_AFTER_TAX');
}
Just add somethings like "echo '<br/>'; after "echo $this->currencyHelper->format($price->price_value_with_tax,$price->price_currency_id);" to put the price without tax under the price with tax