App for product upgrades ? by Damian Rushworth

Hi

Looking for an app or something within shopify to enable me to add product upgrades.

If you look at the site below, you can add upgrades from drop down menus, which are then added to an order and increase the overall cost of the item.

http://www.refreshedbyus.com/dell-optiplex-780-3-0-desktop

ive played around with variants but dont seem able to get it to work like the site above.

any help would be appeciated.

my site www.itzoo.co.uk

thanks

Damian