Thanks for replying.
I don't think that cart.tpl is the right place for this (correct me if I'm wrong), because I want the right quantity directly on product details page. Here's the actual page, btw:
http://www.vinser.eu/store/product.php?productid=1
I'd like the "quantity" drop-down in "Options" section just below the product price to reflect 6/12/18 instead of 1,2,3,4,5,etc.
Adding a product "pack of 6 bottles" is also something different to what I'm seeking for.
Is there any way I can have drop-down on product details page display quantities with the base of 6 ?
TIA