What are the advantages to using K2 over the standard Joomla article CMS?
see the desc here
getk2.org/
k2 when coupled with sigpro and all videos provides rich content with no other extensions or components an it will live alongside joomla content, as well as outside ecommerce solutions.
K2 has integrations for two ecommerce systems that use the k2 content for the display of merchandise
K2mart
www.joomlaworks.net/extensions/commercial-premium/k2mart for virtumart integration
and
K2Store
k2store.org/