you need to move to pro grade equipment. (think 1500+)
However, it doesn't sound like you are that dependent on having ultra clear video. I would borrow someones first and see if the lower level ccd cameras will get you what you are looking for.
The problem isn't money, its the size of the sensors. Same issue I'm having with my Nikon D60 still camera. When you start cramming more pixels on the same size sensor, it simply takes a lot more light to make it work.