Dammy,
I do wish you the best of luck with that. vBulletin and it's surrounding packages really is the "iPhone of CMS's". With Amiga.org, I decided to go ahead and bite the bullet, hoping that people would tolerate the massive changes.
So far, everyone has been able to adapt far better than I could have ever expected but even with all the help (which I am eternally grateful for) it'll take a while to recoup the initial investment.
For me, it was the initial $180, plus my decision that I needed the project management tools (the bug tracker, $60, which I take full bite on that cost because it was my need, and my decision).
Also on the consideration list, if I can't find something better to do the links engine and the news engine is vBAdvanced Dynamics (vbadvanced.com) which, for a multi-instance license is $79 and the vBSEO package to help us with the search engine friendly stuff. That however is a nasty $179, so it'd have to be able to help out a hell of a lot for that much money.
Despite what people might think, costs a lot to run a web site eh? Guess no one ever said hobbies are cheap..
Wayne