I've been running on VB 3.x for quite some time with my community (2007, originally on 3.5) and am considering a move to either IPB or XenForo. There were a number of difficulties with vb 3.x, mostly considering the size of the posts database (677K thread, 26M posts). How does XenForo's search system (and system in general) hold up to a posts database of this size? I was able to integrate Sphinx because anything else was unmanageable. Is there a possibility of a Sphinx backend?