You can customization in phtml file for display number of products for a guest. Do the following steps for customize phtml file.
In the toolbar block you will see
app/code/core/Mage/Catalog/Block/Product/List/Toolbar.php
There is a method:
Public function setCollection($collection);
Inside there is a piece of code:
$limit= (int)$this->get Limit();
If ($limit) {
$this ->_collection->setPageSize($limit);
}
You have to change variable $limit; you should override that block in the local pool, not change
directly in the core. In order to see whether the customer is a guest, you can use this code
Mage:: getSingleton(‘customer/session’) -> isLoggedIn()
