Honestly, I would recommend staying current with the releases, as there are numerous bugfixes that go into even the .0 releases. 6.7.1 is the most current, with 6.7.2 right around the corner.
You can find a list of the new features since your release at
https://www.ubbcentral.com/support/version.php?product=UBB.classic I know there is a special running on Member's Area renewals right now, I'm not sure when it expires...
