The main problem with using a colour graphic display is the abilty to redraw the display fast without you seeing the display update. Each pixel has to have an RGB value sent to it,so with 320x240 resolution you would need to send 230400 bytes to redraw the entire display. So I would recomend using a 64Mhz pic and the paralell interface in 8bit mode on the display for speed. These displays dont have any built in fonts so you will have to make your own.

Sphere.