I've said it before on here. Implement some sort of "Supporting Member" status where you pay a minimal monthly fee for added privileges such as larger sig, more PM space, hell even make reps count for more. Try that and see how much money you make from members willing to pay $1.50 a month to keep IA how they want it compared to selling out for some sponsor.

We did the same system on WRXatlanta and it works very well. We only have a handful of sponsors so it made a very large difference, on here maybe not so much but any money is still money in your pocket.