To illustrate what the others have said regarding maximizing profit from existing traffic, My smallest site is similar to yours at about 100 pages but consistantly earns two to three times what your's does with... half as many visitors. With your number of visitors, that site might easily see four to six times your revenue.
Making your entry/landing page as compelling as possible so that the visitor feels a need to investigate your content more thourghtly will bring your average page views per visit up from two to the ten to twelve I regularly see on that site.
Like your's, it's a niche hobby site (quite obscure as well). I'm not sure just how much more traffic I can expect to get after six years but I've done everything I can think of to be appealing to each person that seeks this site out and extend their vist to the max.
Traffic is important, but it isn't everything!