MathJaX can be configured to convert MathML in to something readable by the browser. If the user/browser likes MathML then it passes it through, if the user/browser prefers HTML+CSS then MathJaX converts it. Thus you can get the "attractive rendering of mathematical symbols (as in MathJax)" by using a TeXish-to-MathML converter and then having MathJaX on top of that.
There are certain advantages of this, the main one being that for those enlightened enough to prefer MathML then MathJaX does nothing meaning that the pages render super-fast (compared to the time it takes when MathJaX has to convert from TeX-like syntax). Thus the "MathJaX or converters" is not necessarily an exclusive or.
In addition, the "attractive rendering" that you attribute to MathJaX is actually due to your browser. MathJaX's role is to present the material in a manner that the browser can understand and, of course, it does so so that it is "attractively rendered". But since it the browser that does the rendering, if you present a static page with the same information then it will be rendered just as attractively (and with considerably less overhead and faster load times).
With regard to a wiki with good maths support, I can heartily recommend Instiki. This is the wiki used by the nLab and there's a lot of mathematics on those pages! The maths conversion is done by a program called itextomml. Specifically to your question, it supports the aligned environment so the equivalent of \begin{align} ... \end{align} is $$\begin{aligned} ... \end{aligned}$$ (which is perfectly good in AMSMath as well).
In addition, I'm a TeX addict and find writing wiki-pages a little arduous, especially when they go over about what would be a page in TeX. So I've written a LaTeX class which does its best to convert genuine LaTeX to the right syntax to be inputted to Instiki, or wordpress, or blosxom, or ... you name it, it could be adapted to that. As an example, the article at this nlab page is the result of converting a LaTeX document (written by someone else, and written before it was thought to include it in the nLab). All of my blog posts on our TeX-SX blog are actually LaTeX documents that were converted to a format appropriate for Wordpress. As it is actually a LaTeX class, it can cope with user-defined macros and other stuff which is hard for a non-TeX-based converter to deal with.
<section></section>tag, which you can then decorate with appropriate CSS. I found this the easiest on something similar that I am working with. – Yiannis Lazarides Aug 28 '11 at 20:00