Paul,
OneSaas should be able to accommodate the Quickbooks accounting integration for sales from the VirtueMart site and eBay. Our Amazon integration is still pending, a few months away, but will be available by early next year at the latest. I am not 100% clear on the other data elements that you would want integrated and with what other services, but it looks like if you want customer contact data integrated with e.g. an external CRM and/or email marketing, our service would do that as well. Let me know if I missed anything in your diagram that is critical to what you are looking for.
Cheers,
Jeff