You can try to implement it with VBulletin (
http://www.vbulletin.com ) and VBPortal(
http://www.911pc.com/ which is a crossbreed of PHPNuke, Weblog, and VBulletin.
VBulletin allows importing from UBB. However, since many servers cannot support PHP because of course many servers are out of date, you may be limited to UBB (as it is the widely compatiable-platform board). Many users of UBB are not able to find PHP and SQL hosting (either insane pricing or limited choices) and use UBB to ensure compatibiity.
[ April 30, 2001 11:43 PM: Message edited by: Myriad ]