Thanks for the response.
"Enable Ajax Cart On Multi Product Variants On Catalog Pages" nowhere to be seen in the admin settgins.
I'm using version 2.5. Is that a new feature in a later version?
How do you allow for multiple product variants to appear in the ajax pop up box like in this example here: http://demos.nop-templates.com/electronics (product is Canon Digital Rebel XSi 12.2 MP Digital SLR Camera)