DVD Studio Pro Menu Still Image Quality Help

Hi, I am trying to import photographs into DVD studio pro... only every time I look at the final output the picture quality is not up to par (blurry, sometimes noticeable pixelation).

The problem, I think, is that my original photo is about 3000 pixels by 2000. In order to get that into 720x480 required for 4:3 dv, I have to downscale it tremendously. I have tried changing size via photoshop (using bicubic sharper from image size), using genuine fractals, and using graphic converter (lamcoz). I have tried sharpening before, after, I have tried anti-aliasing. My final step for each was dragging it into a photoshop ntsc dv canvas and then exporting to tiff uncompressed.

I am thinking that if I could sort this out, once I drag that it into dvd studio pro, it'll be fine. Does anyone have any tips?

Thanks.