You can't. If
DIYMA continues to increase in terms of it's membership size, it will get stupider and stupider, just like all sites. The human race is not a pretty thing to behold and with a large enough sample, you get to see just how retarded we are.
From experience as an admin and moderator on several other forums, the best type of moderator is the one that no one knows too much about. Well known moderators that post a lot will eventually say or do something that will bother someone who has too much free time. Also, there's no need (especially with such a large member base) to have a moderator who knows a lot about car audio; you just need a moderator that can moderate (I know, real weird concept). The only exception to this would be if there was an attempt to collaborate and compile a knowledge base (which I don't know why this site hasn't done considering the minds at work here).
Being a part of a website's staff is one of the most thankless things you will ever do. I enjoy doing it because you can take a certain sense of pride in helping to improve or maintain a body of work, but don't bother signing up if you're looking for e-cool points.