Do you support installation and use of PHPBB?
We have one touch installs for XMB, PHPBB, and Invisionboard. Here are some links to some conversion scripts:
For PHPBB:
http://www.phpbb.com/downloads.php#converters
For XMB:
There are none that I'm aware of. (support for XMB isn't the greatest from their community)
For InvisionBoard:
http://www.invisionboard.com/?resources
This way, you should be able to convert to something faster and more efficient without losing your existing database. :)