I use a special build of osCommerce (OSC) for the sites that I develop. ZenCart is nice, but has trouble applying new contributions that are developed for OSC. The "out of the box" version of OSC may meet you needs, but I would use a version with lots of contributions already installed. Customizing the templates will get away from the "OSC look".

Some urls of OSC sites:
* www.pixiechix.com
* www.parentrecords.com
* www.lhstyle.com
* www.jubilee-designs.com
* www.jubilee-designs.com/catalog2
* www.thejewelrymaster.com