If you want to offer the big money, Vbulletin would be the solution. Pretty simple, and also simple to add skins or mods to.
PhpBB is free, and pretty much as good as vbulletin. It is a bit harder adding mods and skins though. There's more template edits than on VB.
Both phpbb and vbulletin is easy to setup, but then again vbulletin is easier with a lot of things.
So, you gotta choose if you want to do the free solution phpbb, which is pretty easy to setup, or vbulletin which is 300 USD (i believe) and a bit easier, and less template editing that on phpbb
Also, if you need help setting it up, i can do it for you. I've setup both phpbb forums, vbulletin forums, wordpress sites etc.