I think the best way to improve performance, is to make VBO's or DL's for different parts of the map, and render the visible ones. It's much faster than rendering the tiles one by one (That's what you are doing now, right?). But this requires your map to be preprocessed at the beginning. It requires some work, and i don't know if it's worth your time.

I can't tell whether phoenix is good or not. But it might be quite some work to port all your graphics code to Phoenix. It might be very beneficial though. I suppose you do some research before you try to apply any drastic changes to your code.