With 24MB dedicated to graphics you could do even 1080p@32bit, if you want, as you just need 8MB for the frame buffer, but you'd got 16MB left and you'd have to choose how to use them: double buffering would require another 8MB, for example. If you want to better other aspects of graphics quality than simple resolution, RAM matters, frame buffers, double buffers, z-buffers all eat a fixed amount of RAM at a given res and bit depth, so you must take into account how much free RAM for other graphics features you need and decide which res you can afford accordingly.