Ask HN: ECommerce, CRM, ERP – any recommendations?

Looking for free or commercial open source projects like Apache OFBiz or Dolibarr that will allow me to extend it's functionality quite easily (readable code with good documentation or support). Another key feature that I need or will need to add is a single back office system to manage multiple online stores from one place.

Been digging for quite a while already, but there is thousands solutions. Can you recommend any worth looking at?