Something else to consider...

It seems vBulletin has problems when threads get over 250 total posts. We have many threads way over that. Consider the Today's Smokes thread with over 2500 replies. You might want to consider setting the board to lock threads at 250 and folks just have to create new threads. I am a member of several boards using vBulletin that have had to do that to keep the forums from slowing to a constant crawl.