Before I buy XenForo, I need to know one thing: I have a custom built PHP website (symfony 2 based) with it's own user management system. Will I be able to automatically login users in the forum if they are logged in on the main site. I mean is there a possibility to have something like Vanilla's Proxy Connect (or jsConnect)? I don't want to use XenForo's login, sign up system. The users just need to be logged in.