Scanlines isn't such a good idea, because on a TV we can have 768x576 (full Interlaced PAL), but PSX only typically uses half that, ie 288 lines in PAL, or 240 lines in NTSC. Both are drawn at 50 or 60 Hz. The GP2X only has 240 lines, so 320x240 at 60 Hz is the ultimate goal.