Preview image in the Image adjustment window

I have a HP S20 photoscanner. The preview image in the image adjustment
window is only about 490 x 330 pixels. It is too small, I think, when you
have to manipulate sharpness, brightness, colour etc. before the final
scanning.
Now I'm fancy to a Minolta scanner "DiMAGE Scan Elite 5400", but I don't
know if it gives a better and bigger "preview-image" than the HP S20
scanner.
Hope someone in this group can tell me that.
Kind regards
Steffen, Denmark