Wiki appware recommendation?

I need some wiki-ware that meets some specific requirements, and I’d appreciate input from any experienced users. The Wikipedia page here seems to list most of the options but it’s very time-consuming to go through all of them, read their own support pages and try to make any judgment about overall suitability.

I have a rather elderly informational site that I originally constructed in straight HTML - it was the best solution at the time. However, it quickly became difficult to manage the pages and links with such an elementary approach.

So I stopped and installed TikiWiki, which had a billion features I could use to serve the site’s needs… but after putting too much work into it, I realized it was eating almost a half-gig of server space, far more than I could afford for just the appware itself with a ton of media still to come. So I tore it down and left the old site.

Now I want to take another swing at it. I am familiar with TikiWiki and DokuWiki and have glanced at MediaWiki (the basis for Wikipedia). I’d like whatever I use to have the following characteristics:

[ul]
[li]Run on an Apache server.[/li][li]Be relatively lean and efficient.[/li][li]Have current support and updates.[/li][li]Preferably be GNU/GPL but reasonable payware is an option.[/li][li]Have substantial appearance customization, preferably to the level of a WordPress theme. (I can hack and write theme code, so all it has to do is support the feature and have a few close basic themes available.)[/li][li]Be happy running in locked (no public edit) mode for basically one editor. (Some are inherently open/multi-user to the point where they limp if you try to limit the access.)[/li][li]Use a SQL database. (Self-DB models are probably not robust enough to handle the scale of what I want to do; I am also not sure what other db models I can use on my host. I know MySQL.)[/li][/ul]
Leading contenders are DokuWiki, but I think it uses a proprietary db and I am not sure how skinnable/themable it is. Ditto for MediaWiki, which I know is robust enough but doesn’t seem to support themes or single-user mode very well.
Thanks for input.