I have some info that I can offer.
Yes, Tangerine is a Sage VAR for X3. They built a dashboard system - originally called Nectari - for X3. It sold like hotcakes and Sage has OEM'ed the product.
There is currently an integration of X3, the newly released integration for Sage 300, and I believe soon, there will be integrations for Sage CRM and Sage 100.
Is it confusing? Yes but I have seen the SEI product in action. It's extremely slick and I'm looking forward to the integration with Sage CRM.
I'm not sure what happens in the future with the various products. Sage needs to address that shortly, I would hope ...