Hey, 'scuse me jumping in :) but I'm confused. How do you think it is going to help promote this wiki to create another one? If anything, it will reduce the chances of you getting good search engine results (hopefully not too much, because Google usually gives good placement to Wikia communities)
A new wiki with the same people on both would also mean that people would have to edit twice! I don't think that will happen easily.
Of course, I could have misunderstood totally how you are going to use this new wiki, I do that sometimes ;)