Setting up an enterprise wiki

For over a month now, I've tried out (or tried to try out) over a dozen wiki solutions to see what fits my requirements for a knowledge management system for my team at office. The idea is to start small and then grow it one step at a time to include the entire geographically-distributed organization.

I'm absolutely sold on the fact that wiki is the way to go. The flexibility it offers for everyone involved to participate and contribute to the content - which is the key to a successful knowledge management initiative - is unparalleled. The problem though, is that I can't seem to find one single solution that scores well on all fronts without costing a bomb. It's a small team that I'm launching the initiative with and do not want to invest in thousands of dollars on Confluence and the likes.

Wikimedia, probably the first option that comes to mind thanks to the phenomenon that wikipedia is, is easy to set up on a server (I'm no techie and would ideally want something as easy as, say wordpress, to set up and start using), but way too difficult to use. Twiki & Dekiwiki, which seem to provide the ease of use I'm looking for, are too difficult to set up. I'm not a linux guy and getting these wikis set up on windows seems like a herculean task. The rest of them, if easy to use AND set up, are either hosted (not a good solution for critical, confidential, internal information) or far less attractive! I should note here that the I'm setting it up for a team of graphic designers and therefore good looks is high on priority.

So here I am, wondering what to do. Wondering whether I am actually looking in the right places at all. Hoping to see Google do something nice with Jotspot - and providing it's pro services for free - and end my search for an easy-to-use & easy-to-set-up enterprise knowledge management wiki solution.