We have a very advanced E-Commerce solution that has been integrated by and used by many large enterprises. The source code is included so you don't have any vendor lock-in.
We use Java so you are operating system independent and we use the modern Spring/Hibernate/Solr/Velocity architecture on a standard Apache/Tomcat/Mysql|Oracle base. If you prefer Weblogic or other java app servers that is not a problem. Our specialty is customizing and integrating our software to meet your needs and your deadlines.
We can work 3 ways. Either you do all the work, we do all the work or our teams work together. We have offices globally with senior technical resources and project managers in Canada. Our sysadmins and templating staff are in Panama and we have Development and QA at our offices in Ukraine and China. We also have partners with different specialty that we can recommend. Typically all work is done remotely with the exception of an initial set of onsite meetings (if needed) at the start of a project. We use Skype to keep the team integrated and found instant messaging, email and conference calls to work well. For large projects additional face to face meetings are sometimes needed as well.